# Struct std::string::String 1.0.0[−][src]

    pub struct String { /* fields omitted */ }

A UTF-8 encoded, growable string.

The `String` type is the most common string type that has ownership over the contents of the string. It has a close relationship with its borrowed counterpart, the primitive `str`.

# Examples

You can create a `String` from a literal string with `String::from`:

    let hello = String::from("Hello, world!");Run

You can append a `char` to a `String` with the `push` method, and append a `&str` with the `push_str` method:

    let mut hello = String::from("Hello, ");

    hello.push('w');
    hello.push_str("orld!");Run

If you have a vector of UTF-8 bytes, you can create a `String` from it with the `from_utf8` method:

    // some bytes, in a vector
    let sparkle_heart = vec![240, 159, 146, 150];

    // We know these bytes are valid, so we'll use `unwrap()`.
    let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();

    assert_eq!("💖", sparkle_heart);Run

# UTF-8

`String`s are always valid UTF-8. This has a few implications, the first of which is that if you need a non-UTF-8 string, consider `OsString`. It is similar, but without the UTF-8 constraint. The second implication is that you cannot index into a `String`:

ⓘThis example deliberately fails to compile

    let s = "hello";

    println!("The first letter of s is {}", s[0]); // ERROR!!!Run

Indexing is intended to be a constant-time operation, but UTF-8 encoding does not allow us to do this. Furthermore, it's not clear what sort of thing the index should return: a byte, a codepoint, or a grapheme cluster. The `bytes` and `chars` methods return iterators over the first two, respectively.

# Deref

`String`s implement `Deref``<Target=str>`, and so inherit all of `str`'s methods. In addition, this means that you can pass a `String` to a function which takes a `&str` by using an ampersand (`&`):

    fn takes_str(s: &str) { }

    let s = String::from("Hello");

    takes_str(&s);Run

This will create a `&str` from the `String` and pass it in. This conversion is very inexpensive, and so generally, functions will accept `&str`s as arguments unless they need a `String` for some specific reason.

In certain cases Rust doesn't have enough information to make this conversion, known as `Deref` coercion. In the following example a string slice `&'a str` implements the trait `TraitExample`, and the function `example_func` takes anything that implements the trait. In this case Rust would need to make two implicit conversions, which Rust doesn't have the means to do. For that reason, the following example will not compile.

ⓘThis example deliberately fails to compile

    trait TraitExample {}

    impl<'a> TraitExample for &'a str {}

    fn example_func<A: TraitExample>(example_arg: A) {}

    fn main() {
        let example_string = String::from("example_string");
        example_func(&example_string);
    }Run

There are two options that would work instead. The first would be to change the line `example_func(&example_string);` to `example_func(example_string.as_str());`, using the method `as_str()` to explicitly extract the string slice containing the string. The second way changes `example_func(&example_string);` to `example_func(&*example_string);`. In this case we are dereferencing a `String` to a `str`, then referencing the `str` back to `&str`. The second way is more idiomatic, however both work to do the conversion explicitly rather than relying on the implicit conversion.

# Representation

A `String` is made up of three components: a pointer to some bytes, a length, and a capacity. The pointer points to an internal buffer `String` uses to store its data. The length is the number of bytes currently stored in the buffer, and the capacity is the size of the buffer in bytes. As such, the length will always be less than or equal to the capacity.

This buffer is always stored on the heap.

You can look at these with the `as_ptr`, `len`, and `capacity` methods:

    use std::mem;

    let story = String::from("Once upon a time...");

    let ptr = story.as_ptr();
    let len = story.len();
    let capacity = story.capacity();

    // story has nineteen bytes
    assert_eq!(19, len);

    // Now that we have our parts, we throw the story away.
    mem::forget(story);

    // We can re-build a String out of ptr, len, and capacity. This is all
    // unsafe because we are responsible for making sure the components are
    // valid:
    let s = unsafe { String::from_raw_parts(ptr as *mut _, len, capacity) } ;

    assert_eq!(String::from("Once upon a time..."), s);Run

If a `String` has enough capacity, adding elements to it will not re-allocate. For example, consider this program:

    let mut s = String::new();

    println!("{}", s.capacity());

    for _ in 0..5 {
        s.push_str("hello");
        println!("{}", s.capacity());
    }Run

This will output the following:

    0
    5
    10
    20
    20
    40

At first, we have no memory allocated at all, but as we append to the string, it increases its capacity appropriately. If we instead use the `with_capacity` method to allocate the correct capacity initially:

    let mut s = String::with_capacity(25);

    println!("{}", s.capacity());

    for _ in 0..5 {
        s.push_str("hello");
        println!("{}", s.capacity());
    }Run

We end up with a different output:

    25
    25
    25
    25
    25
    25

Here, there's no need to allocate more memory inside the loop.

## Methods

###

`impl String`

[src]

####

`pub const fn new() -> String`

[src]

Creates a new empty `String`.

Given that the `String` is empty, this will not allocate any initial buffer. While that means that this initial operation is very inexpensive, it may cause excessive allocation later when you add data. If you have an idea of how much data the `String` will hold, consider the `with_capacity` method to prevent excessive re-allocation.

# Examples

Basic usage:

    let s = String::new();Run

####

`pub fn with_capacity(capacity: usize) -> String`

[src]

Creates a new empty `String` with a particular capacity.

`String`s have an internal buffer to hold their data. The capacity is the length of that buffer, and can be queried with the `capacity` method. This method creates an empty `String`, but one with an initial buffer that can hold `capacity` bytes. This is useful when you may be appending a bunch of data to the `String`, reducing the number of reallocations it needs to do.

If the given capacity is `0`, no allocation will occur, and this method is identical to the `new` method.

# Examples

Basic usage:

    let mut s = String::with_capacity(10);

    // The String contains no chars, even though it has capacity for more
    assert_eq!(s.len(), 0);

    // These are all done without reallocating...
    let cap = s.capacity();
    for i in 0..10 {
        s.push('a');
    }

    assert_eq!(s.capacity(), cap);

    // ...but this may make the vector reallocate
    s.push('a');Run

####

`pub fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error>`

[src]

Converts a vector of bytes to a `String`.

A string slice (`&str`) is made of bytes (`u8`), and a vector of bytes (`Vec<u8>`) is made of bytes, so this function converts between the two. Not all byte slices are valid `String`s, however: `String` requires that it is valid UTF-8. `from_utf8()` checks to ensure that the bytes are valid UTF-8, and then does the conversion.

If you are sure that the byte slice is valid UTF-8, and you don't want to incur the overhead of the validity check, there is an unsafe version of this function, `from_utf8_unchecked`, which has the same behavior but skips the check.

This method will take care to not copy the vector, for efficiency's sake.

If you need a `&str` instead of a `String`, consider `str::from_utf8`.

The inverse of this method is `as_bytes`.

# Errors

Returns `Err` if the slice is not UTF-8 with a description as to why the provided bytes are not UTF-8. The vector you moved in is also included.

# Examples

Basic usage:

    // some bytes, in a vector
    let sparkle_heart = vec![240, 159, 146, 150];

    // We know these bytes are valid, so we'll use `unwrap()`.
    let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();

    assert_eq!("💖", sparkle_heart);Run

Incorrect bytes:

    // some invalid bytes, in a vector
    let sparkle_heart = vec![0, 159, 146, 150];

    assert!(String::from_utf8(sparkle_heart).is_err());Run

See the docs for `FromUtf8Error` for more details on what you can do with this error.

####

`pub fn from_utf8_lossy(v: &'a [u8]) -> Cow<'a, str>`

[src]

Converts a slice of bytes to a string, including invalid characters.

Strings are made of bytes (`u8`), and a slice of bytes (`&[u8]`) is made of bytes, so this function converts between the two. Not all byte slices are valid strings, however: strings are required to be valid UTF-8. During this conversion, `from_utf8_lossy()` will replace any invalid UTF-8 sequences with `U+FFFD REPLACEMENT CHARACTER`, which looks like this: �

If you are sure that the byte slice is valid UTF-8, and you don't want to incur the overhead of the conversion, there is an unsafe version of this function, `from_utf8_unchecked`, which has the same behavior but skips the checks.

This function returns a `Cow<'a, str>`. If our byte slice is invalid UTF-8, then we need to insert the replacement characters, which will change the size of the string, and hence, require a `String`. But if it's already valid UTF-8, we don't need a new allocation. This return type allows us to handle both cases.

# Examples

Basic usage:

    // some bytes, in a vector
    let sparkle_heart = vec![240, 159, 146, 150];

    let sparkle_heart = String::from_utf8_lossy(&sparkle_heart);

    assert_eq!("💖", sparkle_heart);Run

Incorrect bytes:

    // some invalid bytes
    let input = b"Hello \xF0\x90\x80World";
    let output = String::from_utf8_lossy(input);

    assert_eq!("Hello �World", output);Run

####

`pub fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error>`

[src]

Decode a UTF-16 encoded vector `v` into a `String`, returning `Err` if `v` contains any invalid data.

# Examples

Basic usage:

    // 𝄞music
    let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
              0x0073, 0x0069, 0x0063];
    assert_eq!(String::from("𝄞music"),
               String::from_utf16(v).unwrap());

    // 𝄞mu<invalid>ic
    let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
              0xD800, 0x0069, 0x0063];
    assert!(String::from_utf16(v).is_err());Run

####

`pub fn from_utf16_lossy(v: &[u16]) -> String`

[src]

Decode a UTF-16 encoded slice `v` into a `String`, replacing invalid data with the replacement character (U+FFFD).

Unlike `from_utf8_lossy` which returns a `Cow<'a, str>`, `from_utf16_lossy` returns a `String` since the UTF-16 to UTF-8 conversion requires a memory allocation.

# Examples

Basic usage:

    // 𝄞mus<invalid>ic<invalid>
    let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
              0x0073, 0xDD1E, 0x0069, 0x0063,
              0xD834];

    assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
               String::from_utf16_lossy(v));Run

####

`pub unsafe fn from_raw_parts( buf: *mut u8, length: usize, capacity: usize ) -> String`

[src]

Creates a new `String` from a length, capacity, and pointer.

# Safety

This is highly unsafe, due to the number of invariants that aren't checked:

- The memory at `ptr` needs to have been previously allocated by the same allocator the standard library uses.
- `length` needs to be less than or equal to `capacity`.
- `capacity` needs to be the correct value.

Violating these may cause problems like corrupting the allocator's internal data structures.

The ownership of `ptr` is effectively transferred to the `String` which may then deallocate, reallocate or change the contents of memory pointed to by the pointer at will. Ensure that nothing else uses the pointer after calling this function.

# Examples

Basic usage:

    use std::mem;

    unsafe {
        let s = String::from("hello");
        let ptr = s.as_ptr();
        let len = s.len();
        let capacity = s.capacity();

        mem::forget(s);

        let s = String::from_raw_parts(ptr as *mut _, len, capacity);

        assert_eq!(String::from("hello"), s);
    }Run

####

`pub unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String`

[src]

Converts a vector of bytes to a `String` without checking that the string contains valid UTF-8.

See the safe version, `from_utf8`, for more details.

# Safety

This function is unsafe because it does not check that the bytes passed to it are valid UTF-8. If this constraint is violated, it may cause memory unsafety issues with future users of the `String`, as the rest of the standard library assumes that `String`s are valid UTF-8.

# Examples

Basic usage:

    // some bytes, in a vector
    let sparkle_heart = vec![240, 159, 146, 150];

    let sparkle_heart = unsafe {
        String::from_utf8_unchecked(sparkle_heart)
    };

    assert_eq!("💖", sparkle_heart);Run

####
ⓘImportant traits for Vec<u8>

### Important traits for Vec<u8>

`impl Write for Vec<u8>`

`pub fn into_bytes(self) -> Vec<u8>`

[src]

Converts a `String` into a byte vector.

This consumes the `String`, so we do not need to copy its contents.

# Examples

Basic usage:

    let s = String::from("hello");
    let bytes = s.into_bytes();

    assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]);Run

####

`pub fn as_str(&self) -> &str`

1.7.0
[src]

Extracts a string slice containing the entire string.

# Examples

Basic usage:

    let s = String::from("foo");

    assert_eq!("foo", s.as_str());Run

####

`pub fn as_mut_str(&mut self) -> &mut str`

1.7.0
[src]

Converts a `String` into a mutable string slice.

# Examples

Basic usage:

    let mut s = String::from("foobar");
    let s_mut_str = s.as_mut_str();

    s_mut_str.make_ascii_uppercase();

    assert_eq!("FOOBAR", s_mut_str);Run

####

`pub fn push_str(&mut self, string: &str)`

[src]

Appends a given string slice onto the end of this `String`.

# Examples

Basic usage:

    let mut s = String::from("foo");

    s.push_str("bar");

    assert_eq!("foobar", s);Run

####

`pub fn capacity(&self) -> usize`

[src]

Returns this `String`'s capacity, in bytes.

# Examples

Basic usage:

    let s = String::with_capacity(10);

    assert!(s.capacity() >= 10);Run

####

`pub fn reserve(&mut self, additional: usize)`

[src]

Ensures that this `String`'s capacity is at least `additional` bytes larger than its length.

The capacity may be increased by more than `additional` bytes if it chooses, to prevent frequent reallocations.

If you do not want this "at least" behavior, see the `reserve_exact` method.

# Panics

Panics if the new capacity overflows `usize`.

# Examples

Basic usage:

    let mut s = String::new();

    s.reserve(10);

    assert!(s.capacity() >= 10);Run

This may not actually increase the capacity:

    let mut s = String::with_capacity(10);
    s.push('a');
    s.push('b');

    // s now has a length of 2 and a capacity of 10
    assert_eq!(2, s.len());
    assert_eq!(10, s.capacity());

    // Since we already have an extra 8 capacity, calling this...
    s.reserve(8);

    // ... doesn't actually increase.
    assert_eq!(10, s.capacity());Run

####

`pub fn reserve_exact(&mut self, additional: usize)`

[src]

Ensures that this `String`'s capacity is `additional` bytes larger than its length.

Consider using the `reserve` method unless you absolutely know better than the allocator.

# Panics

Panics if the new capacity overflows `usize`.

# Examples

Basic usage:

    let mut s = String::new();

    s.reserve_exact(10);

    assert!(s.capacity() >= 10);Run

This may not actually increase the capacity:

    let mut s = String::with_capacity(10);
    s.push('a');
    s.push('b');

    // s now has a length of 2 and a capacity of 10
    assert_eq!(2, s.len());
    assert_eq!(10, s.capacity());

    // Since we already have an extra 8 capacity, calling this...
    s.reserve_exact(8);

    // ... doesn't actually increase.
    assert_eq!(10, s.capacity());Run

####

`pub fn try_reserve( &mut self, additional: usize ) -> Result<(), CollectionAllocErr>`

[src]

🔬 This is a nightly-only experimental API. (`try_reserve` #48043)

new API

Tries to reserve capacity for at least `additional` more elements to be inserted in the given `String`. The collection may reserve more space to avoid frequent reallocations. After calling `reserve`, capacity will be greater than or equal to `self.len() + additional`. Does nothing if capacity is already sufficient.

# Errors

If the capacity overflows, or the allocator reports a failure, then an error is returned.

# Examples

    #![feature(try_reserve)]
    use std::collections::CollectionAllocErr;

    fn process_data(data: &str) -> Result<String, CollectionAllocErr> {
        let mut output = String::new();

        // Pre-reserve the memory, exiting if we can't
        output.try_reserve(data.len())?;

        // Now we know this can't OOM in the middle of our complex work
        output.push_str(data);

        Ok(output)
    }Run

####

`pub fn try_reserve_exact( &mut self, additional: usize ) -> Result<(), CollectionAllocErr>`

[src]

🔬 This is a nightly-only experimental API. (`try_reserve` #48043)

new API

Tries to reserves the minimum capacity for exactly `additional` more elements to be inserted in the given `String`. After calling `reserve_exact`, capacity will be greater than or equal to `self.len() + additional`. Does nothing if the capacity is already sufficient.

Note that the allocator may give the collection more space than it requests. Therefore capacity can not be relied upon to be precisely minimal. Prefer `reserve` if future insertions are expected.

# Errors

If the capacity overflows, or the allocator reports a failure, then an error is returned.

# Examples

    #![feature(try_reserve)]
    use std::collections::CollectionAllocErr;

    fn process_data(data: &str) -> Result<String, CollectionAllocErr> {
        let mut output = String::new();

        // Pre-reserve the memory, exiting if we can't
        output.try_reserve(data.len())?;

        // Now we know this can't OOM in the middle of our complex work
        output.push_str(data);

        Ok(output)
    }Run

####

`pub fn shrink_to_fit(&mut self)`

[src]

Shrinks the capacity of this `String` to match its length.

# Examples

Basic usage:

    let mut s = String::from("foo");

    s.reserve(100);
    assert!(s.capacity() >= 100);

    s.shrink_to_fit();
    assert_eq!(3, s.capacity());Run

####

`pub fn shrink_to(&mut self, min_capacity: usize)`

[src]

🔬 This is a nightly-only experimental API. (`shrink_to`)

new API

Shrinks the capacity of this `String` with a lower bound.

The capacity will remain at least as large as both the length and the supplied value.

Panics if the current capacity is smaller than the supplied minimum capacity.

# Examples

    #![feature(shrink_to)]
    let mut s = String::from("foo");

    s.reserve(100);
    assert!(s.capacity() >= 100);

    s.shrink_to(10);
    assert!(s.capacity() >= 10);
    s.shrink_to(0);
    assert!(s.capacity() >= 3);Run

####

`pub fn push(&mut self, ch: char)`

[src]

Appends the given `char` to the end of this `String`.

# Examples

Basic usage:

    let mut s = String::from("abc");

    s.push('1');
    s.push('2');
    s.push('3');

    assert_eq!("abc123", s);Run

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`pub fn as_bytes(&self) -> &[u8]`

[src]

Returns a byte slice of this `String`'s contents.

The inverse of this method is `from_utf8`.

# Examples

Basic usage:

    let s = String::from("hello");

    assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes());Run

####

`pub fn truncate(&mut self, new_len: usize)`

[src]

Shortens this `String` to the specified length.

If `new_len` is greater than the string's current length, this has no effect.

Note that this method has no effect on the allocated capacity of the string

# Panics

Panics if `new_len` does not lie on a `char` boundary.

# Examples

Basic usage:

    let mut s = String::from("hello");

    s.truncate(2);

    assert_eq!("he", s);Run

####

`pub fn pop(&mut self) -> Option<char>`

[src]

Removes the last character from the string buffer and returns it.

Returns `None` if this `String` is empty.

# Examples

Basic usage:

    let mut s = String::from("foo");

    assert_eq!(s.pop(), Some('o'));
    assert_eq!(s.pop(), Some('o'));
    assert_eq!(s.pop(), Some('f'));

    assert_eq!(s.pop(), None);Run

####

`pub fn remove(&mut self, idx: usize) -> char`

[src]

Removes a `char` from this `String` at a byte position and returns it.

This is an `O(n)` operation, as it requires copying every element in the buffer.

# Panics

Panics if `idx` is larger than or equal to the `String`'s length, or if it does not lie on a `char` boundary.

# Examples

Basic usage:

    let mut s = String::from("foo");

    assert_eq!(s.remove(0), 'f');
    assert_eq!(s.remove(1), 'o');
    assert_eq!(s.remove(0), 'o');Run

####

`pub fn retain<F>(&mut self, f: F) where F: FnMut(char) -> bool,`

1.26.0
[src]

Retains only the characters specified by the predicate.

In other words, remove all characters `c` such that `f(c)` returns `false`. This method operates in place and preserves the order of the retained characters.

# Examples

    let mut s = String::from("f_o_ob_ar");

    s.retain(|c| c != '_');

    assert_eq!(s, "foobar");Run

####

`pub fn insert(&mut self, idx: usize, ch: char)`

[src]

Inserts a character into this `String` at a byte position.

This is an `O(n)` operation as it requires copying every element in the buffer.

# Panics

Panics if `idx` is larger than the `String`'s length, or if it does not lie on a `char` boundary.

# Examples

Basic usage:

    let mut s = String::with_capacity(3);

    s.insert(0, 'f');
    s.insert(1, 'o');
    s.insert(2, 'o');

    assert_eq!("foo", s);Run

####

`pub fn insert_str(&mut self, idx: usize, string: &str)`

1.16.0
[src]

Inserts a string slice into this `String` at a byte position.

This is an `O(n)` operation as it requires copying every element in the buffer.

# Panics

Panics if `idx` is larger than the `String`'s length, or if it does not lie on a `char` boundary.

# Examples

Basic usage:

    let mut s = String::from("bar");

    s.insert_str(0, "foo");

    assert_eq!("foobar", s);Run

####
ⓘImportant traits for Vec<u8>

### Important traits for Vec<u8>

`impl Write for Vec<u8>`

`pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8>`

[src]

Returns a mutable reference to the contents of this `String`.

# Safety

This function is unsafe because it does not check that the bytes passed to it are valid UTF-8. If this constraint is violated, it may cause memory unsafety issues with future users of the `String`, as the rest of the standard library assumes that `String`s are valid UTF-8.

# Examples

Basic usage:

    let mut s = String::from("hello");

    unsafe {
        let vec = s.as_mut_vec();
        assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]);

        vec.reverse();
    }
    assert_eq!(s, "olleh");Run

####

`pub fn len(&self) -> usize`

[src]

Returns the length of this `String`, in bytes.

# Examples

Basic usage:

    let a = String::from("foo");

    assert_eq!(a.len(), 3);Run

####

`pub fn is_empty(&self) -> bool`

[src]

Returns `true` if this `String` has a length of zero.

Returns `false` otherwise.

# Examples

Basic usage:

    let mut v = String::new();
    assert!(v.is_empty());

    v.push('a');
    assert!(!v.is_empty());Run

####

`pub fn split_off(&mut self, at: usize) -> String`

1.16.0
[src]

Splits the string into two at the given index.

Returns a newly allocated `String`. `self` contains bytes `[0, at)`, and the returned `String` contains bytes `[at, len)`. `at` must be on the boundary of a UTF-8 code point.

Note that the capacity of `self` does not change.

# Panics

Panics if `at` is not on a `UTF-8` code point boundary, or if it is beyond the last code point of the string.

# Examples

    let mut hello = String::from("Hello, World!");
    let world = hello.split_off(7);
    assert_eq!(hello, "Hello, ");
    assert_eq!(world, "World!");Run

####

`pub fn clear(&mut self)`

[src]

Truncates this `String`, removing all contents.

While this means the `String` will have a length of zero, it does not touch its capacity.

# Examples

Basic usage:

    let mut s = String::from("foo");

    s.clear();

    assert!(s.is_empty());
    assert_eq!(0, s.len());
    assert_eq!(3, s.capacity());Run

####
ⓘImportant traits for Drain<'a>

### Important traits for Drain<'a>

`impl<'a> Iterator for Drain<'a> type Item = char;`

`pub fn drain<R>(&mut self, range: R) -> Drain where R: RangeBounds<usize>,`

1.6.0
[src]

Creates a draining iterator that removes the specified range in the string and yields the removed chars.

Note: The element range is removed even if the iterator is not consumed until the end.

# Panics

Panics if the starting point or end point do not lie on a `char` boundary, or if they're out of bounds.

# Examples

Basic usage:

    let mut s = String::from("α is alpha, β is beta");
    let beta_offset = s.find('β').unwrap_or(s.len());

    // Remove the range up until the β from the string
    let t: String = s.drain(..beta_offset).collect();
    assert_eq!(t, "α is alpha, ");
    assert_eq!(s, "β is beta");

    // A full range clears the string
    s.drain(..);
    assert_eq!(s, "");Run

####

`pub fn replace_range<R>(&mut self, range: R, replace_with: &str) where R: RangeBounds<usize>,`

1.27.0
[src]

Removes the specified range in the string, and replaces it with the given string. The given string doesn't need to be the same length as the range.

# Panics

Panics if the starting point or end point do not lie on a `char` boundary, or if they're out of bounds.

# Examples

Basic usage:

    let mut s = String::from("α is alpha, β is beta");
    let beta_offset = s.find('β').unwrap_or(s.len());

    // Replace the range up until the β from the string
    s.replace_range(..beta_offset, "Α is capital alpha; ");
    assert_eq!(s, "Α is capital alpha; β is beta");Run

####
ⓘImportant traits for Box<I>

### Important traits for Box<I>

`impl<I> Iterator for Box<I> where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>`

`pub fn into_boxed_str(self) -> Box<str>`

1.4.0
[src]

Converts this `String` into a `Box``<``str``>`.

This will drop any excess capacity.

# Examples

Basic usage:

    let s = String::from("hello");

    let b = s.into_boxed_str();Run

## Methods from Deref<Target = str>

####

`pub const fn len(&self) -> usize`

[src]

Returns the length of `self`.

This length is in bytes, not `char`s or graphemes. In other words, it may not be what a human considers the length of the string.

# Examples

Basic usage:

    let len = "foo".len();
    assert_eq!(3, len);

    let len = "ƒoo".len(); // fancy f!
    assert_eq!(4, len);Run

####

`pub const fn is_empty(&self) -> bool`

[src]

Returns `true` if `self` has a length of zero bytes.

# Examples

Basic usage:

    let s = "";
    assert!(s.is_empty());

    let s = "not empty";
    assert!(!s.is_empty());Run

####

`pub fn is_char_boundary(&self, index: usize) -> bool`

1.9.0
[src]

Checks that `index`-th byte lies at the start and/or end of a UTF-8 code point sequence.

The start and end of the string (when `index == self.len()`) are considered to be boundaries.

Returns `false` if `index` is greater than `self.len()`.

# Examples

    let s = "Löwe 老虎 Léopard";
    assert!(s.is_char_boundary(0));
    // start of `老`
    assert!(s.is_char_boundary(6));
    assert!(s.is_char_boundary(s.len()));

    // second byte of `ö`
    assert!(!s.is_char_boundary(2));

    // third byte of `老`
    assert!(!s.is_char_boundary(8));Run

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`pub const fn as_bytes(&self) -> &[u8]`

[src]

Converts a string slice to a byte slice. To convert the byte slice back into a string slice, use the `str::from_utf8` function.

# Examples

Basic usage:

    let bytes = "bors".as_bytes();
    assert_eq!(b"bors", bytes);Run

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`pub unsafe fn as_bytes_mut(&mut self) -> &mut [u8]`

1.20.0
[src]

Converts a mutable string slice to a mutable byte slice. To convert the mutable byte slice back into a mutable string slice, use the `str::from_utf8_mut` function.

# Examples

Basic usage:

    let mut s = String::from("Hello");
    let bytes = unsafe { s.as_bytes_mut() };

    assert_eq!(b"Hello", bytes);Run

Mutability:

    let mut s = String::from("🗻∈🌏");

    unsafe {
        let bytes = s.as_bytes_mut();

        bytes[0] = 0xF0;
        bytes[1] = 0x9F;
        bytes[2] = 0x8D;
        bytes[3] = 0x94;
    }

    assert_eq!("🍔∈🌏", s);Run

####

`pub const fn as_ptr(&self) -> *const u8`

[src]

Converts a string slice to a raw pointer.

As string slices are a slice of bytes, the raw pointer points to a `u8`. This pointer will be pointing to the first byte of the string slice.

# Examples

Basic usage:

    let s = "Hello";
    let ptr = s.as_ptr();Run

####

`pub fn get<I>(&self, i: I) -> Option<&<I as SliceIndex<str>>::Output> where I: SliceIndex<str>,`

1.20.0
[src]

Returns a subslice of `str`.

This is the non-panicking alternative to indexing the `str`. Returns `None` whenever equivalent indexing operation would panic.

# Examples

    let v = String::from("🗻∈🌏");

    assert_eq!(Some("🗻"), v.get(0..4));

    // indices not on UTF-8 sequence boundaries
    assert!(v.get(1..).is_none());
    assert!(v.get(..8).is_none());

    // out of bounds
    assert!(v.get(..42).is_none());Run

####

`pub fn get_mut<I>( &mut self, i: I ) -> Option<&mut <I as SliceIndex<str>>::Output> where I: SliceIndex<str>,`

1.20.0
[src]

Returns a mutable subslice of `str`.

This is the non-panicking alternative to indexing the `str`. Returns `None` whenever equivalent indexing operation would panic.

# Examples

    let mut v = String::from("hello");
    // correct length
    assert!(v.get_mut(0..5).is_some());
    // out of bounds
    assert!(v.get_mut(..42).is_none());
    assert_eq!(Some("he"), v.get_mut(0..2).map(|v| &*v));

    assert_eq!("hello", v);
    {
        let s = v.get_mut(0..2);
        let s = s.map(|s| {
            s.make_ascii_uppercase();
            &*s
        });
        assert_eq!(Some("HE"), s);
    }
    assert_eq!("HEllo", v);Run

####

`pub unsafe fn get_unchecked<I>(&self, i: I) -> &<I as SliceIndex<str>>::Output where I: SliceIndex<str>,`

1.20.0
[src]

Returns a unchecked subslice of `str`.

This is the unchecked alternative to indexing the `str`.

# Safety

Callers of this function are responsible that these preconditions are satisfied:

- The starting index must come before the ending index;
- Indexes must be within bounds of the original slice;
- Indexes must lie on UTF-8 sequence boundaries.

Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the `str` type.

# Examples

    let v = "🗻∈🌏";
    unsafe {
        assert_eq!("🗻", v.get_unchecked(0..4));
        assert_eq!("∈", v.get_unchecked(4..7));
        assert_eq!("🌏", v.get_unchecked(7..11));
    }Run

####

`pub unsafe fn get_unchecked_mut<I>( &mut self, i: I ) -> &mut <I as SliceIndex<str>>::Output where I: SliceIndex<str>,`

1.20.0
[src]

Returns a mutable, unchecked subslice of `str`.

This is the unchecked alternative to indexing the `str`.

# Safety

Callers of this function are responsible that these preconditions are satisfied:

- The starting index must come before the ending index;
- Indexes must be within bounds of the original slice;
- Indexes must lie on UTF-8 sequence boundaries.

Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the `str` type.

# Examples

    let mut v = String::from("🗻∈🌏");
    unsafe {
        assert_eq!("🗻", v.get_unchecked_mut(0..4));
        assert_eq!("∈", v.get_unchecked_mut(4..7));
        assert_eq!("🌏", v.get_unchecked_mut(7..11));
    }Run

####

`pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str`

[src]

Deprecated since 1.29.0

: use `get_unchecked(begin..end)` instead

Creates a string slice from another string slice, bypassing safety checks.

This is generally not recommended, use with caution! For a safe alternative see `str` and `Index`.

This new slice goes from `begin` to `end`, including `begin` but excluding `end`.

To get a mutable string slice instead, see the `slice_mut_unchecked` method.

# Safety

Callers of this function are responsible that three preconditions are satisfied:

- `begin` must come before `end`.
- `begin` and `end` must be byte positions within the string slice.
- `begin` and `end` must lie on UTF-8 sequence boundaries.

# Examples

Basic usage:

    let s = "Löwe 老虎 Léopard";

    unsafe {
        assert_eq!("Löwe 老虎 Léopard", s.slice_unchecked(0, 21));
    }

    let s = "Hello, world!";

    unsafe {
        assert_eq!("world", s.slice_unchecked(7, 12));
    }Run

####

`pub unsafe fn slice_mut_unchecked( &mut self, begin: usize, end: usize ) -> &mut str`

1.5.0
[src]

Deprecated since 1.29.0

: use `get_unchecked_mut(begin..end)` instead

Creates a string slice from another string slice, bypassing safety checks. This is generally not recommended, use with caution! For a safe alternative see `str` and `IndexMut`.

This new slice goes from `begin` to `end`, including `begin` but excluding `end`.

To get an immutable string slice instead, see the `slice_unchecked` method.

# Safety

Callers of this function are responsible that three preconditions are satisfied:

- `begin` must come before `end`.
- `begin` and `end` must be byte positions within the string slice.
- `begin` and `end` must lie on UTF-8 sequence boundaries.

####

`pub fn split_at(&self, mid: usize) -> (&str, &str)`

1.4.0
[src]

Divide one string slice into two at an index.

The argument, `mid`, should be a byte offset from the start of the string. It must also be on the boundary of a UTF-8 code point.

The two slices returned go from the start of the string slice to `mid`, and from `mid` to the end of the string slice.

To get mutable string slices instead, see the `split_at_mut` method.

# Panics

Panics if `mid` is not on a UTF-8 code point boundary, or if it is beyond the last code point of the string slice.

# Examples

Basic usage:

    let s = "Per Martin-Löf";

    let (first, last) = s.split_at(3);

    assert_eq!("Per", first);
    assert_eq!(" Martin-Löf", last);Run

####

`pub fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str)`

1.4.0
[src]

Divide one mutable string slice into two at an index.

The argument, `mid`, should be a byte offset from the start of the string. It must also be on the boundary of a UTF-8 code point.

The two slices returned go from the start of the string slice to `mid`, and from `mid` to the end of the string slice.

To get immutable string slices instead, see the `split_at` method.

# Panics

Panics if `mid` is not on a UTF-8 code point boundary, or if it is beyond the last code point of the string slice.

# Examples

Basic usage:

    let mut s = "Per Martin-Löf".to_string();
    {
        let (first, last) = s.split_at_mut(3);
        first.make_ascii_uppercase();
        assert_eq!("PER", first);
        assert_eq!(" Martin-Löf", last);
    }
    assert_eq!("PER Martin-Löf", s);Run

####
ⓘImportant traits for Chars<'a>

### Important traits for Chars<'a>

`impl<'a> Iterator for Chars<'a> type Item = char;`

`pub fn chars(&self) -> Chars`

[src]

Returns an iterator over the `char`s of a string slice.

As a string slice consists of valid UTF-8, we can iterate through a string slice by `char`. This method returns such an iterator.

It's important to remember that `char` represents a Unicode Scalar Value, and may not match your idea of what a 'character' is. Iteration over grapheme clusters may be what you actually want.

# Examples

Basic usage:

    let word = "goodbye";

    let count = word.chars().count();
    assert_eq!(7, count);

    let mut chars = word.chars();

    assert_eq!(Some('g'), chars.next());
    assert_eq!(Some('o'), chars.next());
    assert_eq!(Some('o'), chars.next());
    assert_eq!(Some('d'), chars.next());
    assert_eq!(Some('b'), chars.next());
    assert_eq!(Some('y'), chars.next());
    assert_eq!(Some('e'), chars.next());

    assert_eq!(None, chars.next());Run

Remember, `char`s may not match your human intuition about characters:

    let y = "y̆";

    let mut chars = y.chars();

    assert_eq!(Some('y'), chars.next()); // not 'y̆'
    assert_eq!(Some('\u{0306}'), chars.next());

    assert_eq!(None, chars.next());Run

####
ⓘImportant traits for CharIndices<'a>

### Important traits for CharIndices<'a>

`impl<'a> Iterator for CharIndices<'a> type Item = (usize, char);`

`pub fn char_indices(&self) -> CharIndices`

[src]

Returns an iterator over the `char`s of a string slice, and their positions.

As a string slice consists of valid UTF-8, we can iterate through a string slice by `char`. This method returns an iterator of both these `char`s, as well as their byte positions.

The iterator yields tuples. The position is first, the `char` is second.

# Examples

Basic usage:

    let word = "goodbye";

    let count = word.char_indices().count();
    assert_eq!(7, count);

    let mut char_indices = word.char_indices();

    assert_eq!(Some((0, 'g')), char_indices.next());
    assert_eq!(Some((1, 'o')), char_indices.next());
    assert_eq!(Some((2, 'o')), char_indices.next());
    assert_eq!(Some((3, 'd')), char_indices.next());
    assert_eq!(Some((4, 'b')), char_indices.next());
    assert_eq!(Some((5, 'y')), char_indices.next());
    assert_eq!(Some((6, 'e')), char_indices.next());

    assert_eq!(None, char_indices.next());Run

Remember, `char`s may not match your human intuition about characters:

    let yes = "y̆es";

    let mut char_indices = yes.char_indices();

    assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆')
    assert_eq!(Some((1, '\u{0306}')), char_indices.next());

    // note the 3 here - the last character took up two bytes
    assert_eq!(Some((3, 'e')), char_indices.next());
    assert_eq!(Some((4, 's')), char_indices.next());

    assert_eq!(None, char_indices.next());Run

####
ⓘImportant traits for Bytes<'a>

### Important traits for Bytes<'a>

`impl<'a> Iterator for Bytes<'a> type Item = u8;`

`pub fn bytes(&self) -> Bytes`

[src]

An iterator over the bytes of a string slice.

As a string slice consists of a sequence of bytes, we can iterate through a string slice by byte. This method returns such an iterator.

# Examples

Basic usage:

    let mut bytes = "bors".bytes();

    assert_eq!(Some(b'b'), bytes.next());
    assert_eq!(Some(b'o'), bytes.next());
    assert_eq!(Some(b'r'), bytes.next());
    assert_eq!(Some(b's'), bytes.next());

    assert_eq!(None, bytes.next());Run

####
ⓘImportant traits for SplitWhitespace<'a>

### Important traits for SplitWhitespace<'a>

`impl<'a> Iterator for SplitWhitespace<'a> type Item = &'a str;`

`pub fn split_whitespace(&self) -> SplitWhitespace`

1.1.0
[src]

Split a string slice by whitespace.

The iterator returned will return string slices that are sub-slices of the original string slice, separated by any amount of whitespace.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property `White_Space`. If you only want to split on ASCII whitespace instead, use `split_ascii_whitespace`.

# Examples

Basic usage:

    let mut iter = "A few words".split_whitespace();

    assert_eq!(Some("A"), iter.next());
    assert_eq!(Some("few"), iter.next());
    assert_eq!(Some("words"), iter.next());

    assert_eq!(None, iter.next());Run

All kinds of whitespace are considered:

    let mut iter = " Mary   had\ta\u{2009}little  \n\t lamb".split_whitespace();
    assert_eq!(Some("Mary"), iter.next());
    assert_eq!(Some("had"), iter.next());
    assert_eq!(Some("a"), iter.next());
    assert_eq!(Some("little"), iter.next());
    assert_eq!(Some("lamb"), iter.next());

    assert_eq!(None, iter.next());Run

####
ⓘImportant traits for SplitAsciiWhitespace<'a>

### Important traits for SplitAsciiWhitespace<'a>

`impl<'a> Iterator for SplitAsciiWhitespace<'a> type Item = &'a str;`

`pub fn split_ascii_whitespace(&self) -> SplitAsciiWhitespace`

[src]

🔬 This is a nightly-only experimental API. (`split_ascii_whitespace` #48656)

Split a string slice by ASCII whitespace.

The iterator returned will return string slices that are sub-slices of the original string slice, separated by any amount of ASCII whitespace.

To split by Unicode `Whitespace` instead, use `split_whitespace`.

# Examples

Basic usage:

    #![feature(split_ascii_whitespace)]
    let mut iter = "A few words".split_ascii_whitespace();

    assert_eq!(Some("A"), iter.next());
    assert_eq!(Some("few"), iter.next());
    assert_eq!(Some("words"), iter.next());

    assert_eq!(None, iter.next());Run

All kinds of ASCII whitespace are considered:

    let mut iter = " Mary   had\ta little  \n\t lamb".split_whitespace();
    assert_eq!(Some("Mary"), iter.next());
    assert_eq!(Some("had"), iter.next());
    assert_eq!(Some("a"), iter.next());
    assert_eq!(Some("little"), iter.next());
    assert_eq!(Some("lamb"), iter.next());

    assert_eq!(None, iter.next());Run

####
ⓘImportant traits for Lines<'a>

### Important traits for Lines<'a>

`impl<'a> Iterator for Lines<'a> type Item = &'a str;`

`pub fn lines(&self) -> Lines`

[src]

An iterator over the lines of a string, as string slices.

Lines are ended with either a newline (`\n`) or a carriage return with a line feed (`\r\n`).

The final line ending is optional.

# Examples

Basic usage:

    let text = "foo\r\nbar\n\nbaz\n";
    let mut lines = text.lines();

    assert_eq!(Some("foo"), lines.next());
    assert_eq!(Some("bar"), lines.next());
    assert_eq!(Some(""), lines.next());
    assert_eq!(Some("baz"), lines.next());

    assert_eq!(None, lines.next());Run

The final line ending isn't required:

    let text = "foo\nbar\n\r\nbaz";
    let mut lines = text.lines();

    assert_eq!(Some("foo"), lines.next());
    assert_eq!(Some("bar"), lines.next());
    assert_eq!(Some(""), lines.next());
    assert_eq!(Some("baz"), lines.next());

    assert_eq!(None, lines.next());Run

####
ⓘImportant traits for LinesAny<'a>

### Important traits for LinesAny<'a>

`impl<'a> Iterator for LinesAny<'a> type Item = &'a str;`

`pub fn lines_any(&self) -> LinesAny`

[src]

Deprecated since 1.4.0

: use lines() instead now

An iterator over the lines of a string.

####
ⓘImportant traits for EncodeUtf16<'a>

### Important traits for EncodeUtf16<'a>

`impl<'a> Iterator for EncodeUtf16<'a> type Item = u16;`

`pub fn encode_utf16(&self) -> EncodeUtf16`

1.8.0
[src]

Returns an iterator of `u16` over the string encoded as UTF-16.

# Examples

Basic usage:

    let text = "Zażółć gęślą jaźń";

    let utf8_len = text.len();
    let utf16_len = text.encode_utf16().count();

    assert!(utf16_len <= utf8_len);Run

####

`pub fn contains<'a, P>(&'a self, pat: P) -> bool where P: Pattern<'a>,`

[src]

Returns `true` if the given pattern matches a sub-slice of this string slice.

Returns `false` if it does not.

# Examples

Basic usage:

    let bananas = "bananas";

    assert!(bananas.contains("nana"));
    assert!(!bananas.contains("apples"));Run

####

`pub fn starts_with<'a, P>(&'a self, pat: P) -> bool where P: Pattern<'a>,`

[src]

Returns `true` if the given pattern matches a prefix of this string slice.

Returns `false` if it does not.

# Examples

Basic usage:

    let bananas = "bananas";

    assert!(bananas.starts_with("bana"));
    assert!(!bananas.starts_with("nana"));Run

####

`pub fn ends_with<'a, P>(&'a self, pat: P) -> bool where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,`

[src]

Returns `true` if the given pattern matches a suffix of this string slice.

Returns `false` if it does not.

# Examples

Basic usage:

    let bananas = "bananas";

    assert!(bananas.ends_with("anas"));
    assert!(!bananas.ends_with("nana"));Run

####

`pub fn find<'a, P>(&'a self, pat: P) -> Option<usize> where P: Pattern<'a>,`

[src]

Returns the byte index of the first character of this string slice that matches the pattern.

Returns `None` if the pattern doesn't match.

The pattern can be a `&str`, `char`, or a closure that determines if a character matches.

# Examples

Simple patterns:

    let s = "Löwe 老虎 Léopard";

    assert_eq!(s.find('L'), Some(0));
    assert_eq!(s.find('é'), Some(14));
    assert_eq!(s.find("Léopard"), Some(13));Run

More complex patterns using point-free style and closures:

    let s = "Löwe 老虎 Léopard";

    assert_eq!(s.find(char::is_whitespace), Some(5));
    assert_eq!(s.find(char::is_lowercase), Some(1));
    assert_eq!(s.find(|c: char| c.is_whitespace() || c.is_lowercase()), Some(1));
    assert_eq!(s.find(|c: char| (c < 'o') && (c > 'a')), Some(4));Run

Not finding the pattern:

    let s = "Löwe 老虎 Léopard";
    let x: &[_] = &['1', '2'];

    assert_eq!(s.find(x), None);Run

####

`pub fn rfind<'a, P>(&'a self, pat: P) -> Option<usize> where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,`

[src]

Returns the byte index of the last character of this string slice that matches the pattern.

Returns `None` if the pattern doesn't match.

The pattern can be a `&str`, `char`, or a closure that determines if a character matches.

# Examples

Simple patterns:

    let s = "Löwe 老虎 Léopard";

    assert_eq!(s.rfind('L'), Some(13));
    assert_eq!(s.rfind('é'), Some(14));Run

More complex patterns with closures:

    let s = "Löwe 老虎 Léopard";

    assert_eq!(s.rfind(char::is_whitespace), Some(12));
    assert_eq!(s.rfind(char::is_lowercase), Some(20));Run

Not finding the pattern:

    let s = "Löwe 老虎 Léopard";
    let x: &[_] = &['1', '2'];

    assert_eq!(s.rfind(x), None);Run

####
ⓘImportant traits for Split<'a, P>

### Important traits for Split<'a, P>

`impl<'a, P> Iterator for Split<'a, P> where
P: Pattern<'a>, type Item = &'a str;`

`pub fn split<'a, P>(&'a self, pat: P) -> Split<'a, P> where P: Pattern<'a>,`

[src]

An iterator over substrings of this string slice, separated by characters matched by a pattern.

The pattern can be a `&str`, `char`, or a closure that determines the split.

# Iterator behavior

The returned iterator will be a `DoubleEndedIterator` if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, eg, `char` but not for `&str`.

If the pattern allows a reverse search but its results might differ from a forward search, the `rsplit` method can be used.

# Examples

Simple patterns:

    let v: Vec<&str> = "Mary had a little lamb".split(' ').collect();
    assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);

    let v: Vec<&str> = "".split('X').collect();
    assert_eq!(v, [""]);

    let v: Vec<&str> = "lionXXtigerXleopard".split('X').collect();
    assert_eq!(v, ["lion", "", "tiger", "leopard"]);

    let v: Vec<&str> = "lion::tiger::leopard".split("::").collect();
    assert_eq!(v, ["lion", "tiger", "leopard"]);

    let v: Vec<&str> = "abc1def2ghi".split(char::is_numeric).collect();
    assert_eq!(v, ["abc", "def", "ghi"]);

    let v: Vec<&str> = "lionXtigerXleopard".split(char::is_uppercase).collect();
    assert_eq!(v, ["lion", "tiger", "leopard"]);Run

A more complex pattern, using a closure:

    let v: Vec<&str> = "abc1defXghi".split(|c| c == '1' || c == 'X').collect();
    assert_eq!(v, ["abc", "def", "ghi"]);Run

If a string contains multiple contiguous separators, you will end up with empty strings in the output:

    let x = "||||a||b|c".to_string();
    let d: Vec<_> = x.split('|').collect();

    assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);Run

Contiguous separators are separated by the empty string.

    let x = "(///)".to_string();
    let d: Vec<_> = x.split('/').collect();

    assert_eq!(d, &["(", "", "", ")"]);Run

Separators at the start or end of a string are neighbored by empty strings.

    let d: Vec<_> = "010".split("0").collect();
    assert_eq!(d, &["", "1", ""]);Run

When the empty string is used as a separator, it separates every character in the string, along with the beginning and end of the string.

    let f: Vec<_> = "rust".split("").collect();
    assert_eq!(f, &["", "r", "u", "s", "t", ""]);Run

Contiguous separators can lead to possibly surprising behavior when whitespace is used as the separator. This code is correct:

    let x = "    a  b c".to_string();
    let d: Vec<_> = x.split(' ').collect();

    assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);Run

It does not give you:

ⓘThis example is not tested

    assert_eq!(d, &["a", "b", "c"]);Run

Use `split_whitespace` for this behavior.

####
ⓘImportant traits for RSplit<'a, P>

### Important traits for RSplit<'a, P>

`impl<'a, P> Iterator for RSplit<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, type Item = &'a str;`

`pub fn rsplit<'a, P>(&'a self, pat: P) -> RSplit<'a, P> where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,`

[src]

An iterator over substrings of the given string slice, separated by characters matched by a pattern and yielded in reverse order.

The pattern can be a `&str`, `char`, or a closure that determines the split.

# Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a `DoubleEndedIterator` if a forward/reverse search yields the same elements.

For iterating from the front, the `split` method can be used.

# Examples

Simple patterns:

    let v: Vec<&str> = "Mary had a little lamb".rsplit(' ').collect();
    assert_eq!(v, ["lamb", "little", "a", "had", "Mary"]);

    let v: Vec<&str> = "".rsplit('X').collect();
    assert_eq!(v, [""]);

    let v: Vec<&str> = "lionXXtigerXleopard".rsplit('X').collect();
    assert_eq!(v, ["leopard", "tiger", "", "lion"]);

    let v: Vec<&str> = "lion::tiger::leopard".rsplit("::").collect();
    assert_eq!(v, ["leopard", "tiger", "lion"]);Run

A more complex pattern, using a closure:

    let v: Vec<&str> = "abc1defXghi".rsplit(|c| c == '1' || c == 'X').collect();
    assert_eq!(v, ["ghi", "def", "abc"]);Run

####
ⓘImportant traits for SplitTerminator<'a, P>

### Important traits for SplitTerminator<'a, P>

`impl<'a, P> Iterator for SplitTerminator<'a, P> where
P: Pattern<'a>, type Item = &'a str;`

`pub fn split_terminator<'a, P>(&'a self, pat: P) -> SplitTerminator<'a, P> where P: Pattern<'a>,`

[src]

An iterator over substrings of the given string slice, separated by characters matched by a pattern.

The pattern can be a `&str`, `char`, or a closure that determines the split.

Equivalent to `split`, except that the trailing substring is skipped if empty.

This method can be used for string data that is terminated, rather than separated by a pattern.

# Iterator behavior

The returned iterator will be a `DoubleEndedIterator` if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, eg, `char` but not for `&str`.

If the pattern allows a reverse search but its results might differ from a forward search, the `rsplit_terminator` method can be used.

# Examples

Basic usage:

    let v: Vec<&str> = "A.B.".split_terminator('.').collect();
    assert_eq!(v, ["A", "B"]);

    let v: Vec<&str> = "A..B..".split_terminator(".").collect();
    assert_eq!(v, ["A", "", "B", ""]);Run

####
ⓘImportant traits for RSplitTerminator<'a, P>

### Important traits for RSplitTerminator<'a, P>

`impl<'a, P> Iterator for RSplitTerminator<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, type Item = &'a str;`

`pub fn rsplit_terminator<'a, P>(&'a self, pat: P) -> RSplitTerminator<'a, P> where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,`

[src]

An iterator over substrings of `self`, separated by characters matched by a pattern and yielded in reverse order.

The pattern can be a simple `&str`, `char`, or a closure that determines the split. Additional libraries might provide more complex patterns like regular expressions.

Equivalent to `split`, except that the trailing substring is skipped if empty.

This method can be used for string data that is terminated, rather than separated by a pattern.

# Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be double ended if a forward/reverse search yields the same elements.

For iterating from the front, the `split_terminator` method can be used.

# Examples

    let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect();
    assert_eq!(v, ["B", "A"]);

    let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect();
    assert_eq!(v, ["", "B", "", "A"]);Run

####
ⓘImportant traits for SplitN<'a, P>

### Important traits for SplitN<'a, P>

`impl<'a, P> Iterator for SplitN<'a, P> where
P: Pattern<'a>, type Item = &'a str;`

`pub fn splitn<'a, P>(&'a self, n: usize, pat: P) -> SplitN<'a, P> where P: Pattern<'a>,`

[src]

An iterator over substrings of the given string slice, separated by a pattern, restricted to returning at most `n` items.

If `n` substrings are returned, the last substring (the `n`th substring) will contain the remainder of the string.

The pattern can be a `&str`, `char`, or a closure that determines the split.

# Iterator behavior

The returned iterator will not be double ended, because it is not efficient to support.

If the pattern allows a reverse search, the `rsplitn` method can be used.

# Examples

Simple patterns:

    let v: Vec<&str> = "Mary had a little lambda".splitn(3, ' ').collect();
    assert_eq!(v, ["Mary", "had", "a little lambda"]);

    let v: Vec<&str> = "lionXXtigerXleopard".splitn(3, "X").collect();
    assert_eq!(v, ["lion", "", "tigerXleopard"]);

    let v: Vec<&str> = "abcXdef".splitn(1, 'X').collect();
    assert_eq!(v, ["abcXdef"]);

    let v: Vec<&str> = "".splitn(1, 'X').collect();
    assert_eq!(v, [""]);Run

A more complex pattern, using a closure:

    let v: Vec<&str> = "abc1defXghi".splitn(2, |c| c == '1' || c == 'X').collect();
    assert_eq!(v, ["abc", "defXghi"]);Run

####
ⓘImportant traits for RSplitN<'a, P>

### Important traits for RSplitN<'a, P>

`impl<'a, P> Iterator for RSplitN<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, type Item = &'a str;`

`pub fn rsplitn<'a, P>(&'a self, n: usize, pat: P) -> RSplitN<'a, P> where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,`

[src]

An iterator over substrings of this string slice, separated by a pattern, starting from the end of the string, restricted to returning at most `n` items.

If `n` substrings are returned, the last substring (the `n`th substring) will contain the remainder of the string.

The pattern can be a `&str`, `char`, or a closure that determines the split.

# Iterator behavior

The returned iterator will not be double ended, because it is not efficient to support.

For splitting from the front, the `splitn` method can be used.

# Examples

Simple patterns:

    let v: Vec<&str> = "Mary had a little lamb".rsplitn(3, ' ').collect();
    assert_eq!(v, ["lamb", "little", "Mary had a"]);

    let v: Vec<&str> = "lionXXtigerXleopard".rsplitn(3, 'X').collect();
    assert_eq!(v, ["leopard", "tiger", "lionX"]);

    let v: Vec<&str> = "lion::tiger::leopard".rsplitn(2, "::").collect();
    assert_eq!(v, ["leopard", "lion::tiger"]);Run

A more complex pattern, using a closure:

    let v: Vec<&str> = "abc1defXghi".rsplitn(2, |c| c == '1' || c == 'X').collect();
    assert_eq!(v, ["ghi", "abc1def"]);Run

####
ⓘImportant traits for Matches<'a, P>

### Important traits for Matches<'a, P>

`impl<'a, P> Iterator for Matches<'a, P> where
P: Pattern<'a>, type Item = &'a str;`

`pub fn matches<'a, P>(&'a self, pat: P) -> Matches<'a, P> where P: Pattern<'a>,`

1.2.0
[src]

An iterator over the disjoint matches of a pattern within the given string slice.

The pattern can be a `&str`, `char`, or a closure that determines if a character matches.

# Iterator behavior

The returned iterator will be a `DoubleEndedIterator` if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, eg, `char` but not for `&str`.

If the pattern allows a reverse search but its results might differ from a forward search, the `rmatches` method can be used.

# Examples

Basic usage:

    let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect();
    assert_eq!(v, ["abc", "abc", "abc"]);

    let v: Vec<&str> = "1abc2abc3".matches(char::is_numeric).collect();
    assert_eq!(v, ["1", "2", "3"]);Run

####
ⓘImportant traits for RMatches<'a, P>

### Important traits for RMatches<'a, P>

`impl<'a, P> Iterator for RMatches<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, type Item = &'a str;`

`pub fn rmatches<'a, P>(&'a self, pat: P) -> RMatches<'a, P> where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,`

1.2.0
[src]

An iterator over the disjoint matches of a pattern within this string slice, yielded in reverse order.

The pattern can be a `&str`, `char`, or a closure that determines if a character matches.

# Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a `DoubleEndedIterator` if a forward/reverse search yields the same elements.

For iterating from the front, the `matches` method can be used.

# Examples

Basic usage:

    let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect();
    assert_eq!(v, ["abc", "abc", "abc"]);

    let v: Vec<&str> = "1abc2abc3".rmatches(char::is_numeric).collect();
    assert_eq!(v, ["3", "2", "1"]);Run

####
ⓘImportant traits for MatchIndices<'a, P>

### Important traits for MatchIndices<'a, P>

`impl<'a, P> Iterator for MatchIndices<'a, P> where
P: Pattern<'a>, type Item = (usize, &'a str);`

`pub fn match_indices<'a, P>(&'a self, pat: P) -> MatchIndices<'a, P> where P: Pattern<'a>,`

1.5.0
[src]

An iterator over the disjoint matches of a pattern within this string slice as well as the index that the match starts at.

For matches of `pat` within `self` that overlap, only the indices corresponding to the first match are returned.

The pattern can be a `&str`, `char`, or a closure that determines if a character matches.

# Iterator behavior

The returned iterator will be a `DoubleEndedIterator` if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, eg, `char` but not for `&str`.

If the pattern allows a reverse search but its results might differ from a forward search, the `rmatch_indices` method can be used.

# Examples

Basic usage:

    let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
    assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);

    let v: Vec<_> = "1abcabc2".match_indices("abc").collect();
    assert_eq!(v, [(1, "abc"), (4, "abc")]);

    let v: Vec<_> = "ababa".match_indices("aba").collect();
    assert_eq!(v, [(0, "aba")]); // only the first `aba`Run

####
ⓘImportant traits for RMatchIndices<'a, P>

### Important traits for RMatchIndices<'a, P>

`impl<'a, P> Iterator for RMatchIndices<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, type Item = (usize, &'a str);`

`pub fn rmatch_indices<'a, P>(&'a self, pat: P) -> RMatchIndices<'a, P> where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,`

1.5.0
[src]

An iterator over the disjoint matches of a pattern within `self`, yielded in reverse order along with the index of the match.

For matches of `pat` within `self` that overlap, only the indices corresponding to the last match are returned.

The pattern can be a `&str`, `char`, or a closure that determines if a character matches.

# Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a `DoubleEndedIterator` if a forward/reverse search yields the same elements.

For iterating from the front, the `match_indices` method can be used.

# Examples

Basic usage:

    let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
    assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);

    let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect();
    assert_eq!(v, [(4, "abc"), (1, "abc")]);

    let v: Vec<_> = "ababa".rmatch_indices("aba").collect();
    assert_eq!(v, [(2, "aba")]); // only the last `aba`Run

####

`pub fn trim(&self) -> &str`

[src]

Returns a string slice with leading and trailing whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property `White_Space`.

# Examples

Basic usage:

    let s = " Hello\tworld\t";

    assert_eq!("Hello\tworld", s.trim());Run

####

`pub fn trim_left(&self) -> &str`

[src]

Returns a string slice with leading whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property `White_Space`.

# Text directionality

A string is a sequence of bytes. 'Left' in this context means the first position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the right side, not the left.

# Examples

Basic usage:

    let s = " Hello\tworld\t";

    assert_eq!("Hello\tworld\t", s.trim_left());Run

Directionality:

    let s = "  English";
    assert!(Some('E') == s.trim_left().chars().next());

    let s = "  עברית";
    assert!(Some('ע') == s.trim_left().chars().next());Run

####

`pub fn trim_right(&self) -> &str`

[src]

Returns a string slice with trailing whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property `White_Space`.

# Text directionality

A string is a sequence of bytes. 'Right' in this context means the last position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the left side, not the right.

# Examples

Basic usage:

    let s = " Hello\tworld\t";

    assert_eq!(" Hello\tworld", s.trim_right());Run

Directionality:

    let s = "English  ";
    assert!(Some('h') == s.trim_right().chars().rev().next());

    let s = "עברית  ";
    assert!(Some('ת') == s.trim_right().chars().rev().next());Run

####

`pub fn trim_matches<'a, P>(&'a self, pat: P) -> &'a str where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,`

[src]

Returns a string slice with all prefixes and suffixes that match a pattern repeatedly removed.

The pattern can be a `char` or a closure that determines if a character matches.

# Examples

Simple patterns:

    assert_eq!("11foo1bar11".trim_matches('1'), "foo1bar");
    assert_eq!("123foo1bar123".trim_matches(char::is_numeric), "foo1bar");

    let x: &[_] = &['1', '2'];
    assert_eq!("12foo1bar12".trim_matches(x), "foo1bar");Run

A more complex pattern, using a closure:

    assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");Run

####

`pub fn trim_left_matches<'a, P>(&'a self, pat: P) -> &'a str where P: Pattern<'a>,`

[src]

Returns a string slice with all prefixes that match a pattern repeatedly removed.

The pattern can be a `&str`, `char`, or a closure that determines if a character matches.

# Text directionality

A string is a sequence of bytes. 'Left' in this context means the first position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the right side, not the left.

# Examples

Basic usage:

    assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11");
    assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123");

    let x: &[_] = &['1', '2'];
    assert_eq!("12foo1bar12".trim_left_matches(x), "foo1bar12");Run

####

`pub fn trim_right_matches<'a, P>(&'a self, pat: P) -> &'a str where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,`

[src]

Returns a string slice with all suffixes that match a pattern repeatedly removed.

The pattern can be a `&str`, `char`, or a closure that determines if a character matches.

# Text directionality

A string is a sequence of bytes. 'Right' in this context means the last position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the left side, not the right.

# Examples

Simple patterns:

    assert_eq!("11foo1bar11".trim_right_matches('1'), "11foo1bar");
    assert_eq!("123foo1bar123".trim_right_matches(char::is_numeric), "123foo1bar");

    let x: &[_] = &['1', '2'];
    assert_eq!("12foo1bar12".trim_right_matches(x), "12foo1bar");Run

A more complex pattern, using a closure:

    assert_eq!("1fooX".trim_right_matches(|c| c == '1' || c == 'X'), "1foo");Run

####

`pub fn parse<F>(&self) -> Result<F, <F as FromStr>::Err> where F: FromStr,`

[src]

Parses this string slice into another type.

Because `parse` is so general, it can cause problems with type inference. As such, `parse` is one of the few times you'll see the syntax affectionately known as the 'turbofish': `::<>`. This helps the inference algorithm understand specifically which type you're trying to parse into.

`parse` can parse any type that implements the `FromStr` trait.

# Errors

Will return `Err` if it's not possible to parse this string slice into the desired type.

# Examples

Basic usage

    let four: u32 = "4".parse().unwrap();

    assert_eq!(4, four);Run

Using the 'turbofish' instead of annotating `four`:

    let four = "4".parse::<u32>();

    assert_eq!(Ok(4), four);Run

Failing to parse:

    let nope = "j".parse::<u32>();

    assert!(nope.is_err());Run

####

`pub fn is_ascii(&self) -> bool`

1.23.0
[src]

Checks if all characters in this string are within the ASCII range.

# Examples

    let ascii = "hello!\n";
    let non_ascii = "Grüße, Jürgen ❤";

    assert!(ascii.is_ascii());
    assert!(!non_ascii.is_ascii());Run

####

`pub fn eq_ignore_ascii_case(&self, other: &str) -> bool`

1.23.0
[src]

Checks that two strings are an ASCII case-insensitive match.

Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`, but without allocating and copying temporaries.

# Examples

    assert!("Ferris".eq_ignore_ascii_case("FERRIS"));
    assert!("Ferrös".eq_ignore_ascii_case("FERRöS"));
    assert!(!"Ferrös".eq_ignore_ascii_case("FERRÖS"));Run

####

`pub fn make_ascii_uppercase(&mut self)`

1.23.0
[src]

Converts this string to its ASCII upper case equivalent in-place.

ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', but non-ASCII letters are unchanged.

To return a new uppercased value without modifying the existing one, use `to_ascii_uppercase`.

####

`pub fn make_ascii_lowercase(&mut self)`

1.23.0
[src]

Converts this string to its ASCII lower case equivalent in-place.

ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', but non-ASCII letters are unchanged.

To return a new lowercased value without modifying the existing one, use `to_ascii_lowercase`.

####

`#[must_use = "this returns the replaced string as a new allocation, without modifying the original"] pub fn replace<'a, P>(&'a self, from: P, to: &str) -> String where P: Pattern<'a>,`

[src]

Replaces all matches of a pattern with another string.

`replace` creates a new `String`, and copies the data from this string slice into it. While doing so, it attempts to find matches of a pattern. If it finds any, it replaces them with the replacement string slice.

# Examples

Basic usage:

    let s = "this is old";

    assert_eq!("this is new", s.replace("old", "new"));Run

When the pattern doesn't match:

    let s = "this is old";
    assert_eq!(s, s.replace("cookie monster", "little lamb"));Run

####

`#[must_use = "this returns the replaced string as a new allocation, without modifying the original"] pub fn replacen<'a, P>(&'a self, pat: P, to: &str, count: usize) -> String where P: Pattern<'a>,`

1.16.0
[src]

Replaces first N matches of a pattern with another string.

`replacen` creates a new `String`, and copies the data from this string slice into it. While doing so, it attempts to find matches of a pattern. If it finds any, it replaces them with the replacement string slice at most `count` times.

# Examples

Basic usage:

    let s = "foo foo 123 foo";
    assert_eq!("new new 123 foo", s.replacen("foo", "new", 2));
    assert_eq!("faa fao 123 foo", s.replacen('o', "a", 3));
    assert_eq!("foo foo new23 foo", s.replacen(char::is_numeric, "new", 1));Run

When the pattern doesn't match:

    let s = "this is old";
    assert_eq!(s, s.replacen("cookie monster", "little lamb", 10));Run

####

`pub fn to_lowercase(&self) -> String`

1.2.0
[src]

Returns the lowercase equivalent of this string slice, as a new `String`.

'Lowercase' is defined according to the terms of the Unicode Derived Core Property `Lowercase`.

Since some characters can expand into multiple characters when changing the case, this function returns a `String` instead of modifying the parameter in-place.

# Examples

Basic usage:

    let s = "HELLO";

    assert_eq!("hello", s.to_lowercase());Run

A tricky example, with sigma:

    let sigma = "Σ";

    assert_eq!("σ", sigma.to_lowercase());

    // but at the end of a word, it's ς, not σ:
    let odysseus = "ὈΔΥΣΣΕΎΣ";

    assert_eq!("ὀδυσσεύς", odysseus.to_lowercase());Run

Languages without case are not changed:

    let new_year = "农历新年";

    assert_eq!(new_year, new_year.to_lowercase());Run

####

`pub fn to_uppercase(&self) -> String`

1.2.0
[src]

Returns the uppercase equivalent of this string slice, as a new `String`.

'Uppercase' is defined according to the terms of the Unicode Derived Core Property `Uppercase`.

Since some characters can expand into multiple characters when changing the case, this function returns a `String` instead of modifying the parameter in-place.

# Examples

Basic usage:

    let s = "hello";

    assert_eq!("HELLO", s.to_uppercase());Run

Scripts without case are not changed:

    let new_year = "农历新年";

    assert_eq!(new_year, new_year.to_uppercase());Run

####

`pub fn escape_debug(&self) -> String`

[src]

🔬 This is a nightly-only experimental API. (`str_escape` #27791)

return type may change to be an iterator

Escapes each char in `s` with `char::escape_debug`.

Note: only extended grapheme codepoints that begin the string will be escaped.

####

`pub fn escape_default(&self) -> String`

[src]

🔬 This is a nightly-only experimental API. (`str_escape` #27791)

return type may change to be an iterator

Escapes each char in `s` with `char::escape_default`.

####

`pub fn escape_unicode(&self) -> String`

[src]

🔬 This is a nightly-only experimental API. (`str_escape` #27791)

return type may change to be an iterator

Escapes each char in `s` with `char::escape_unicode`.

####

`pub fn repeat(&self, n: usize) -> String`

1.16.0
[src]

Create a `String` by repeating a string `n` times.

# Panics

This function will panic if the capacity would overflow.

# Examples

Basic usage:

    assert_eq!("abc".repeat(4), String::from("abcabcabcabc"));Run

A panic upon overflow:

    fn main() {
        // this will panic at runtime
        "0123456789abcdef".repeat(usize::max_value());
    }Run

####

`pub fn to_ascii_uppercase(&self) -> String`

1.23.0
[src]

Returns a copy of this string where each character is mapped to its ASCII upper case equivalent.

ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', but non-ASCII letters are unchanged.

To uppercase the value in-place, use `make_ascii_uppercase`.

To uppercase ASCII characters in addition to non-ASCII characters, use `to_uppercase`.

# Examples

    let s = "Grüße, Jürgen ❤";

    assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase());Run

####

`pub fn to_ascii_lowercase(&self) -> String`

1.23.0
[src]

Returns a copy of this string where each character is mapped to its ASCII lower case equivalent.

ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', but non-ASCII letters are unchanged.

To lowercase the value in-place, use `make_ascii_lowercase`.

To lowercase ASCII characters in addition to non-ASCII characters, use `to_lowercase`.

# Examples

    let s = "Grüße, Jürgen ❤";

    assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase());Run

## Trait Implementations

###

`impl Debug for String`

[src]

####

`fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`

[src]

Formats the value using the given formatter. Read more

###

`impl Clone for String`

[src]

####

`fn clone(&self) -> String`

[src]

Returns a copy of the value. Read more

####

`fn clone_from(&mut self, source: &String)`

[src]

Performs copy-assignment from `source`. Read more

###

`impl Index<RangeTo<usize>> for String`

[src]

#### `type Output = str`

The returned type after indexing.

####

`fn index(&self, index: RangeTo<usize>) -> &str`

[src]

Performs the indexing (`container[index]`) operation.

###

`impl Index<RangeFull> for String`

[src]

#### `type Output = str`

The returned type after indexing.

####

`fn index(&self, _index: RangeFull) -> &str`

[src]

Performs the indexing (`container[index]`) operation.

###

`impl Index<Range<usize>> for String`

[src]

#### `type Output = str`

The returned type after indexing.

####

`fn index(&self, index: Range<usize>) -> &str`

[src]

Performs the indexing (`container[index]`) operation.

###

`impl Index<RangeToInclusive<usize>> for String`

1.26.0
[src]

#### `type Output = str`

The returned type after indexing.

####

`fn index(&self, index: RangeToInclusive<usize>) -> &str`

[src]

Performs the indexing (`container[index]`) operation.

###

`impl Index<RangeInclusive<usize>> for String`

1.26.0
[src]

#### `type Output = str`

The returned type after indexing.

####

`fn index(&self, index: RangeInclusive<usize>) -> &str`

[src]

Performs the indexing (`container[index]`) operation.

###

`impl Index<RangeFrom<usize>> for String`

[src]

#### `type Output = str`

The returned type after indexing.

####

`fn index(&self, index: RangeFrom<usize>) -> &str`

[src]

Performs the indexing (`container[index]`) operation.

###

`impl<'a, 'b> PartialEq<&'a str> for String`

[src]

####

`fn eq(&self, other: &&'a str) -> bool`

[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

####

`fn ne(&self, other: &&'a str) -> bool`

[src]

This method tests for `!=`.

###

`impl<'a, 'b> PartialEq<Cow<'a, str>> for String`

[src]

####

`fn eq(&self, other: &Cow<'a, str>) -> bool`

[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

####

`fn ne(&self, other: &Cow<'a, str>) -> bool`

[src]

This method tests for `!=`.

###

`impl PartialEq<String> for String`

[src]

####

`fn eq(&self, other: &String) -> bool`

[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

####

`fn ne(&self, other: &String) -> bool`

[src]

This method tests for `!=`.

###

`impl<'a, 'b> PartialEq<String> for Cow<'a, str>`

[src]

####

`fn eq(&self, other: &String) -> bool`

[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

####

`fn ne(&self, other: &String) -> bool`

[src]

This method tests for `!=`.

###

`impl<'a, 'b> PartialEq<String> for str`

[src]

####

`fn eq(&self, other: &String) -> bool`

[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

####

`fn ne(&self, other: &String) -> bool`

[src]

This method tests for `!=`.

###

`impl<'a, 'b> PartialEq<str> for String`

[src]

####

`fn eq(&self, other: &str) -> bool`

[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

####

`fn ne(&self, other: &str) -> bool`

[src]

This method tests for `!=`.

###

`impl<'a, 'b> PartialEq<String> for &'a str`

[src]

####

`fn eq(&self, other: &String) -> bool`

[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

####

`fn ne(&self, other: &String) -> bool`

[src]

This method tests for `!=`.

###

`impl Write for String`

[src]

####

`fn write_str(&mut self, s: &str) -> Result<(), Error>`

[src]

Writes a slice of bytes into this writer, returning whether the write succeeded. Read more

####

`fn write_char(&mut self, c: char) -> Result<(), Error>`

[src]

Writes a [`char`] into this writer, returning whether the write succeeded. Read more

####

`fn write_fmt(&mut self, args: Arguments) -> Result<(), Error>`

[src]

Glue for usage of the [`write!`] macro with implementors of this trait. Read more

###

`impl ToString for String`

1.17.0
[src]

####

`fn to_string(&self) -> String`

[src]

Converts the given value to a `String`. Read more

###

`impl PartialOrd<String> for String`

[src]

####

`fn partial_cmp(&self, other: &String) -> Option<Ordering>`

[src]

This method returns an ordering between `self` and `other` values if one exists. Read more

####

`fn lt(&self, other: &String) -> bool`

[src]

This method tests less than (for `self` and `other`) and is used by the `<` operator. Read more

####

`fn le(&self, other: &String) -> bool`

[src]

This method tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more

####

`fn gt(&self, other: &String) -> bool`

[src]

This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more

####

`fn ge(&self, other: &String) -> bool`

[src]

This method tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more

###

`impl DerefMut for String`

1.3.0
[src]

####

`fn deref_mut(&mut self) -> &mut str`

[src]

Mutably dereferences the value.

###

`impl Default for String`

[src]

####

`fn default() -> String`

[src]

Creates an empty `String`.

###

`impl<'a> AddAssign<&'a str> for String`

1.12.0
[src]

Implements the `+=` operator for appending to a `String`.

This has the same behavior as the `push_str` method.

####

`fn add_assign(&mut self, other: &str)`

[src]

Performs the `+=` operation.

###

`impl<'a> Add<&'a str> for String`

[src]

Implements the `+` operator for concatenating two strings.

This consumes the `String` on the left-hand side and re-uses its buffer (growing it if necessary). This is done to avoid allocating a new `String` and copying the entire contents on every operation, which would lead to `O(n^2)` running time when building an `n`-byte string by repeated concatenation.

The string on the right-hand side is only borrowed; its contents are copied into the returned `String`.

# Examples

Concatenating two `String`s takes the first by value and borrows the second:

    let a = String::from("hello");
    let b = String::from(" world");
    let c = a + &b;
    // `a` is moved and can no longer be used here.Run

If you want to keep using the first `String`, you can clone it and append to the clone instead:

    let a = String::from("hello");
    let b = String::from(" world");
    let c = a.clone() + &b;
    // `a` is still valid here.Run

Concatenating `&str` slices can be done by converting the first to a `String`:

    let a = "hello";
    let b = " world";
    let c = a.to_string() + b;Run

#### `type Output = String`

The resulting type after applying the `+` operator.

####

`fn add(self, other: &str) -> String`

[src]

Performs the `+` operation.

###

`impl Hash for String`

[src]

####

`fn hash<H>(&self, hasher: &mut H) where H: Hasher,`

[src]

Feeds this value into the given [`Hasher`]. Read more

####

`fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher,`

1.3.0
[src]

Feeds a slice of this type into the given [`Hasher`]. Read more

###

`impl Extend<String> for String`

1.4.0
[src]

####

`fn extend<I>(&mut self, iter: I) where I: IntoIterator<Item = String>,`

[src]

Extends a collection with the contents of an iterator. Read more

###

`impl<'a> Extend<&'a char> for String`

1.2.0
[src]

####

`fn extend<I>(&mut self, iter: I) where I: IntoIterator<Item = &'a char>,`

[src]

Extends a collection with the contents of an iterator. Read more

###

`impl Extend<char> for String`

[src]

####

`fn extend<I>(&mut self, iter: I) where I: IntoIterator<Item = char>,`

[src]

Extends a collection with the contents of an iterator. Read more

###

`impl<'a> Extend<&'a str> for String`

[src]

####

`fn extend<I>(&mut self, iter: I) where I: IntoIterator<Item = &'a str>,`

[src]

Extends a collection with the contents of an iterator. Read more

###

`impl<'a> Extend<Cow<'a, str>> for String`

1.19.0
[src]

####

`fn extend<I>(&mut self, iter: I) where I: IntoIterator<Item = Cow<'a, str>>,`

[src]

Extends a collection with the contents of an iterator. Read more

###

`impl<'a, 'b> Pattern<'a> for &'b String`

[src]

A convenience impl that delegates to the impl for `&str`

#### `type Searcher = <&'b str as Pattern<'a>>::Searcher`

🔬 This is a nightly-only experimental API. (`pattern` #27721)

API not fully fleshed out and ready to be stabilized

Associated searcher for this pattern

####

`fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher`

[src]

🔬 This is a nightly-only experimental API. (`pattern` #27721)

API not fully fleshed out and ready to be stabilized

Constructs the associated searcher from `self` and the `haystack` to search in. Read more

####

`fn is_contained_in(self, haystack: &'a str) -> bool`

[src]

🔬 This is a nightly-only experimental API. (`pattern` #27721)

API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches anywhere in the haystack

####

`fn is_prefix_of(self, haystack: &'a str) -> bool`

[src]

🔬 This is a nightly-only experimental API. (`pattern` #27721)

API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches at the front of the haystack

####

`fn is_suffix_of(self, haystack: &'a str) -> bool where Self::Searcher: ReverseSearcher<'a>,`

[src]

🔬 This is a nightly-only experimental API. (`pattern` #27721)

API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches at the back of the haystack

###

`impl Eq for String`

[src]

###

`impl Display for String`

[src]

####

`fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`

[src]

Formats the value using the given formatter. Read more

###

`impl Ord for String`

[src]

####

`fn cmp(&self, other: &String) -> Ordering`

[src]

This method returns an `Ordering` between `self` and `other`. Read more

####

`fn max(self, other: Self) -> Self`

1.21.0
[src]

Compares and returns the maximum of two values. Read more

####

`fn min(self, other: Self) -> Self`

1.21.0
[src]

Compares and returns the minimum of two values. Read more

###

`impl FromStr for String`

[src]

#### `type Err = ParseError`

The associated error which can be returned from parsing.

####

`fn from_str(s: &str) -> Result<String, ParseError>`

[src]

Parses a string `s` to return a value of this type. Read more

###

`impl IndexMut<RangeFrom<usize>> for String`

1.3.0
[src]

####

`fn index_mut(&mut self, index: RangeFrom<usize>) -> &mut str`

[src]

Performs the mutable indexing (`container[index]`) operation.

###

`impl IndexMut<RangeFull> for String`

1.3.0
[src]

####

`fn index_mut(&mut self, _index: RangeFull) -> &mut str`

[src]

Performs the mutable indexing (`container[index]`) operation.

###

`impl IndexMut<RangeToInclusive<usize>> for String`

1.26.0
[src]

####

`fn index_mut(&mut self, index: RangeToInclusive<usize>) -> &mut str`

[src]

Performs the mutable indexing (`container[index]`) operation.

###

`impl IndexMut<RangeTo<usize>> for String`

1.3.0
[src]

####

`fn index_mut(&mut self, index: RangeTo<usize>) -> &mut str`

[src]

Performs the mutable indexing (`container[index]`) operation.

###

`impl IndexMut<RangeInclusive<usize>> for String`

1.26.0
[src]

####

`fn index_mut(&mut self, index: RangeInclusive<usize>) -> &mut str`

[src]

Performs the mutable indexing (`container[index]`) operation.

###

`impl IndexMut<Range<usize>> for String`

1.3.0
[src]

####

`fn index_mut(&mut self, index: Range<usize>) -> &mut str`

[src]

Performs the mutable indexing (`container[index]`) operation.

###

`impl Borrow<str> for String`

[src]

####

`fn borrow(&self) -> &str`

[src]

Immutably borrows from an owned value. Read more

###

`impl<'a> FromIterator<&'a char> for String`

1.17.0
[src]

####

`fn from_iter<I>(iter: I) -> String where I: IntoIterator<Item = &'a char>,`

[src]

Creates a value from an iterator. Read more

###

`impl FromIterator<char> for String`

[src]

####

`fn from_iter<I>(iter: I) -> String where I: IntoIterator<Item = char>,`

[src]

Creates a value from an iterator. Read more

###

`impl<'a> FromIterator<&'a str> for String`

[src]

####

`fn from_iter<I>(iter: I) -> String where I: IntoIterator<Item = &'a str>,`

[src]

Creates a value from an iterator. Read more

###

`impl<'a> FromIterator<Cow<'a, str>> for String`

1.19.0
[src]

####

`fn from_iter<I>(iter: I) -> String where I: IntoIterator<Item = Cow<'a, str>>,`

[src]

Creates a value from an iterator. Read more

###

`impl FromIterator<String> for String`

1.4.0
[src]

####

`fn from_iter<I>(iter: I) -> String where I: IntoIterator<Item = String>,`

[src]

Creates a value from an iterator. Read more

###

`impl<'a> FromIterator<String> for Cow<'a, str>`

1.12.0
[src]

####

`fn from_iter<I>(it: I) -> Cow<'a, str> where I: IntoIterator<Item = String>,`

[src]

Creates a value from an iterator. Read more

###

`impl AsRef<[u8]> for String`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

`fn as_ref(&self) -> &[u8]`

[src]

Performs the conversion.

###

`impl AsRef<str> for String`

[src]

####

`fn as_ref(&self) -> &str`

[src]

Performs the conversion.

###

`impl From<String> for Box<str>`

1.20.0
[src]

####
ⓘImportant traits for Box<I>

### Important traits for Box<I>

`impl<I> Iterator for Box<I> where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>`

`fn from(s: String) -> Box<str>`

[src]

Performs the conversion.

###

`impl From<String> for Rc<str>`

1.21.0
[src]

####

`fn from(v: String) -> Rc<str>`

[src]

Performs the conversion.

###

`impl<'a> From<String> for Cow<'a, str>`

[src]

####

`fn from(s: String) -> Cow<'a, str>`

[src]

Performs the conversion.

###

`impl<'a> From<&'a String> for Cow<'a, str>`

1.28.0
[src]

####

`fn from(s: &'a String) -> Cow<'a, str>`

[src]

Performs the conversion.

###

`impl<'a> From<&'a str> for String`

[src]

####

`fn from(s: &'a str) -> String`

[src]

Performs the conversion.

###

`impl From<String> for Arc<str>`

1.21.0
[src]

####

`fn from(v: String) -> Arc<str>`

[src]

Performs the conversion.

###

`impl From<String> for Vec<u8>`

1.14.0
[src]

####
ⓘImportant traits for Vec<u8>

### Important traits for Vec<u8>

`impl Write for Vec<u8>`

`fn from(string: String) -> Vec<u8>`

[src]

Performs the conversion.

###

`impl From<Box<str>> for String`

1.18.0
[src]

####

`fn from(s: Box<str>) -> String`

[src]

Performs the conversion.

###

`impl<'a> From<Cow<'a, str>> for String`

1.14.0
[src]

####

`fn from(s: Cow<'a, str>) -> String`

[src]

Performs the conversion.

###

`impl Deref for String`

[src]

#### `type Target = str`

The resulting type after dereferencing.

####

`fn deref(&self) -> &str`

[src]

Dereferences the value.

###

`impl From<String> for Box<Error + Send + Sync>`

[src]

####
ⓘImportant traits for Box<I>

### Important traits for Box<I>

`impl<I> Iterator for Box<I> where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>`

`fn from(err: String) -> Box<Error + Send + Sync>`

[src]

Performs the conversion.

###

`impl From<String> for Box<Error>`

1.6.0
[src]

####
ⓘImportant traits for Box<I>

### Important traits for Box<I>

`impl<I> Iterator for Box<I> where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>`

`fn from(str_err: String) -> Box<Error>`

[src]

Performs the conversion.

###

`impl From<String> for OsString`

[src]

####

`fn from(s: String) -> OsString`

[src]

Performs the conversion.

###

`impl AsRef<OsStr> for String`

[src]

####

`fn as_ref(&self) -> &OsStr`

[src]

Performs the conversion.

###

`impl ToSocketAddrs for String`

1.16.0
[src]

#### `type Iter = IntoIter<SocketAddr>`

Returned iterator over socket addresses which this type may correspond to. Read more

####

`fn to_socket_addrs(&self) -> Result<IntoIter<SocketAddr>>`

[src]

Converts this object to an iterator of resolved `SocketAddr`s. Read more

###

`impl From<String> for PathBuf`

[src]

####

`fn from(s: String) -> PathBuf`

[src]

Performs the conversion.

###

`impl AsRef<Path> for String`

[src]

####

`fn as_ref(&self) -> &Path`

[src]

Performs the conversion.

## Auto Trait Implementations

###

`impl Send for String`

###

`impl Sync for String`

# Help

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