# Struct arduboy_rust::heapless::String

source ·

    pub struct String<const N: usize> { /* private fields */ }

Expand description

A fixed capacity `String`

## Implementations§

source§

### impl<const N: usize> String<N>

source

#### pub const fn new() -> String<N>

Constructs a new, empty `String` with a fixed capacity of `N` bytes

##### Examples

Basic usage:

    use heapless::String;

    // allocate the string on the stack
    let mut s: String<4> = String::new();

    // allocate the string in a static variable
    static mut S: String<4> = String::new();

source

#### pub fn into_bytes(self) -> Vec<u8, N>

Converts a `String` into a byte vector.

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

##### Examples

Basic usage:

    use heapless::String;

    let s: String<4> = String::from("ab");
    let b = s.into_bytes();
    assert!(b.len() == 2);

    assert_eq!(&['a' as u8, 'b' as u8], &b[..]);

source

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

Extracts a string slice containing the entire string.

##### Examples

Basic usage:

    use heapless::String;

    let mut s: String<4> = String::from("ab");
    assert!(s.as_str() == "ab");

    let _s = s.as_str();
    // s.push('c'); // <- cannot borrow `s` as mutable because it is also borrowed as immutable

source

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

Converts a `String` into a mutable string slice.

##### Examples

Basic usage:

    use heapless::String;

    let mut s: String<4> = String::from("ab");
    let s = s.as_mut_str();
    s.make_ascii_uppercase();

source

#### pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8, N>

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 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");

source

#### pub fn push_str(&mut self, string: &str) -> Result<(), ()>

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

##### Examples

Basic usage:

    use heapless::String;

    let mut s: String<8> = String::from("foo");

    assert!(s.push_str("bar").is_ok());

    assert_eq!("foobar", s);

    assert!(s.push_str("tender").is_err());

source

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

Returns the maximum number of elements the String can hold

##### Examples

Basic usage:

    use heapless::String;

    let mut s: String<4> = String::new();
    assert!(s.capacity() == 4);

source

#### pub fn push(&mut self, c: char) -> Result<(), ()>

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

##### Examples

Basic usage:

    use heapless::String;

    let mut s: String<8> = String::from("abc");

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

    assert!("abc123" == s.as_str());

    assert_eq!("abc123", s);

source

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

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:

    use heapless::String;

    let mut s: String<8> = String::from("hello");

    s.truncate(2);

    assert_eq!("he", s);

source

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

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

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

##### Examples

Basic usage:

    use heapless::String;

    let mut s: String<8> = 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);

source

#### pub fn clear(&mut self)

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:

    use heapless::String;

    let mut s: String<8> = String::from("foo");

    s.clear();

    assert!(s.is_empty());
    assert_eq!(0, s.len());
    assert_eq!(8, s.capacity());

## Methods from Deref<Target = str>§

1.0.0

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

Returns the length of `self`.

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

##### Examples

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

    assert_eq!("ƒoo".len(), 4); // fancy f!
    assert_eq!("ƒoo".chars().count(), 3);

1.0.0

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

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

##### Examples

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

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

1.9.0

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

Checks that `index`-th byte is the first byte in a UTF-8 code point sequence or the end of the string.

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));

#### pub fn floor_char_boundary(&self, index: usize) -> usize

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

Finds the closest `x` not exceeding `index` where `is_char_boundary(x)` is `true`.

This method can help you truncate a string so that it’s still valid UTF-8, but doesn’t exceed a given number of bytes. Note that this is done purely at the character level and can still visually split graphemes, even though the underlying characters aren’t split. For example, the emoji 🧑‍🔬 (scientist) could be split so that the string only includes 🧑 (person) instead.

##### Examples

    #![feature(round_char_boundary)]
    let s = "❤️🧡💛💚💙💜";
    assert_eq!(s.len(), 26);
    assert!(!s.is_char_boundary(13));

    let closest = s.floor_char_boundary(13);
    assert_eq!(closest, 10);
    assert_eq!(&s[..closest], "❤️🧡");

#### pub fn ceil_char_boundary(&self, index: usize) -> usize

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

Finds the closest `x` not below `index` where `is_char_boundary(x)` is `true`.

This method is the natural complement to `floor_char_boundary`. See that method for more details.

##### Panics

Panics if `index > self.len()`.

##### Examples

    #![feature(round_char_boundary)]
    let s = "❤️🧡💛💚💙💜";
    assert_eq!(s.len(), 26);
    assert!(!s.is_char_boundary(13));

    let closest = s.ceil_char_boundary(13);
    assert_eq!(closest, 14);
    assert_eq!(&s[..closest], "❤️🧡💛");

1.0.0

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

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

##### Examples

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

1.20.0

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

Converts a mutable string slice to a mutable byte slice.

##### Safety

The caller must ensure that the content of the slice is valid UTF-8 before the borrow ends and the underlying `str` is used.

Use of a `str` whose contents are not valid UTF-8 is undefined behavior.

##### Examples

Basic usage:

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

    assert_eq!(b"Hello", bytes);

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);

1.0.0

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

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.

The caller must ensure that the returned pointer is never written to. If you need to mutate the contents of the string slice, use `as_mut_ptr`.

##### Examples

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

1.36.0

#### pub fn as_mut_ptr(&mut self) -> *mut u8

Converts a mutable 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.

It is your responsibility to make sure that the string slice only gets modified in a way that it remains valid UTF-8.

1.20.0

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

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());

1.20.0

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

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);

1.20.0

#### pub unsafe fn get_unchecked<I>(&self, i: I) -> &<I as SliceIndex<str>>::Outputwhere I: SliceIndex<str>,

Returns an 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 not exceed 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));
    }

1.20.0

#### pub unsafe fn get_unchecked_mut<I>( &mut self, i: I ) -> &mut <I as SliceIndex<str>>::Outputwhere I: SliceIndex<str>,

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 not exceed 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));
    }

1.0.0

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

👎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 not exceed `end`.
- `begin` and `end` must be byte positions within the string slice.
- `begin` and `end` must lie on UTF-8 sequence boundaries.

##### Examples

    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));
    }

1.5.0

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

👎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 not exceed `end`.
- `begin` and `end` must be byte positions within the string slice.
- `begin` and `end` must lie on UTF-8 sequence boundaries.

1.4.0

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

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 past the end of the last code point of the string slice.

##### Examples

    let s = "Per Martin-Löf";

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

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

1.4.0

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

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 past the end of the last code point of the string slice.

##### Examples

    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);

1.0.0

#### pub fn chars(&self) -> Chars<'_>

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 might not match your idea of what a ‘character’ is. Iteration over grapheme clusters may be what you actually want. This functionality is not provided by Rust’s standard library, check crates.io instead.

##### 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());

Remember, `char`s might not match your 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());

1.0.0

#### pub fn char_indices(&self) -> CharIndices<'_>

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());

Remember, `char`s might not match your 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());

1.0.0

#### pub fn bytes(&self) -> Bytes<'_>

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

    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());

1.1.0

#### pub fn split_whitespace(&self) -> SplitWhitespace<'_>

Splits 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());

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());

If the string is empty or all whitespace, the iterator yields no string slices:

    assert_eq!("".split_whitespace().next(), None);
    assert_eq!("   ".split_whitespace().next(), None);

1.34.0

#### pub fn split_ascii_whitespace(&self) -> SplitAsciiWhitespace<'_>

Splits 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:

    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());

All kinds of ASCII whitespace are considered:

    let mut iter = " Mary   had\ta little  \n\t lamb".split_ascii_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());

If the string is empty or all ASCII whitespace, the iterator yields no string slices:

    assert_eq!("".split_ascii_whitespace().next(), None);
    assert_eq!("   ".split_ascii_whitespace().next(), None);

1.0.0

#### pub fn lines(&self) -> Lines<'_>

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

Lines are split at line endings that are either newlines (`\n`) or sequences of a carriage return followed by a line feed (`\r\n`).

Line terminators are not included in the lines returned by the iterator.

Note that any carriage return (`\r`) not immediately followed by a line feed (`\n`) does not split a line. These carriage returns are thereby included in the produced lines.

The final line ending is optional. A string that ends with a final line ending will return the same lines as an otherwise identical string without a final line ending.

##### Examples

Basic usage:

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

    assert_eq!(Some("foo"), lines.next());
    assert_eq!(Some("bar"), lines.next());
    assert_eq!(Some(""), lines.next());
    // Trailing carriage return is included in the last line
    assert_eq!(Some("baz\r"), lines.next());

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

The final line does not require any ending:

    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());

1.0.0

#### pub fn lines_any(&self) -> LinesAny<'_>

👎Deprecated since 1.4.0: use lines() instead now

An iterator over the lines of a string.

1.8.0

#### pub fn encode_utf16(&self) -> EncodeUtf16<'_>

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

##### Examples

    let text = "Zażółć gęślą jaźń";

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

    assert!(utf16_len <= utf8_len);

1.0.0

#### pub fn contains<'a, P>(&'a self, pat: P) -> boolwhere P: Pattern<'a>,

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

Returns `false` if it does not.

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

##### Examples

    let bananas = "bananas";

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

1.0.0

#### pub fn starts_with<'a, P>(&'a self, pat: P) -> boolwhere P: Pattern<'a>,

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

Returns `false` if it does not.

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

##### Examples

    let bananas = "bananas";

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

1.0.0

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

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

Returns `false` if it does not.

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

##### Examples

    let bananas = "bananas";

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

1.0.0

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

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`, a slice of `char`s, or a function or closure that determines if a character matches.

##### Examples

Simple patterns:

    let s = "Löwe 老虎 Léopard Gepardi";

    assert_eq!(s.find('L'), Some(0));
    assert_eq!(s.find('é'), Some(14));
    assert_eq!(s.find("pard"), Some(17));

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));

Not finding the pattern:

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

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

1.0.0

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

Returns the byte index for the first character of the last match of the pattern in this string slice.

Returns [`None`] if the pattern doesn’t match.

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

##### Examples

Simple patterns:

    let s = "Löwe 老虎 Léopard Gepardi";

    assert_eq!(s.rfind('L'), Some(13));
    assert_eq!(s.rfind('é'), Some(14));
    assert_eq!(s.rfind("pard"), Some(24));

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));

Not finding the pattern:

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

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

1.0.0

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

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

The pattern can be a `&str`, `char`, a slice of `char`s, or a function or 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, e.g., `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"]);

If the pattern is a slice of chars, split on each occurrence of any of the characters:

    let v: Vec<&str> = "2020-11-03 23:59".split(&['-', ' ', ':', '@'][..]).collect();
    assert_eq!(v, ["2020", "11", "03", "23", "59"]);

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"]);

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"]);

Contiguous separators are separated by the empty string.

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

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

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", ""]);

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", ""]);

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"]);

It does not give you:

ⓘ

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

Use `split_whitespace` for this behavior.

1.51.0

#### pub fn split_inclusive<'a, P>(&'a self, pat: P) -> SplitInclusive<'a, P>where P: Pattern<'a>,

An iterator over substrings of this string slice, separated by characters matched by a pattern. Differs from the iterator produced by `split` in that `split_inclusive` leaves the matched part as the terminator of the substring.

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

##### Examples

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

If the last element of the string is matched, that element will be considered the terminator of the preceding substring. That substring will be the last item returned by the iterator.

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

1.0.0

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

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`, a slice of `char`s, or a function or 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 `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"]);

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"]);

1.0.0

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

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

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

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, e.g., `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

    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", ""]);

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

1.0.0

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

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

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

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"]);

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

1.0.0

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

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`, a slice of `char`s, or a function or closure that determines if a character matches.

##### 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, [""]);

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"]);

1.0.0

#### 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>,

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`, a slice of `char`s, or a function or closure that determines if a character matches.

##### 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"]);

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"]);

1.52.0

#### pub fn split_once<'a, P>(&'a self, delimiter: P) -> Option<(&'a str, &'a str)>where P: Pattern<'a>,

Splits the string on the first occurrence of the specified delimiter and returns prefix before delimiter and suffix after delimiter.

##### Examples

    assert_eq!("cfg".split_once('='), None);
    assert_eq!("cfg=".split_once('='), Some(("cfg", "")));
    assert_eq!("cfg=foo".split_once('='), Some(("cfg", "foo")));
    assert_eq!("cfg=foo=bar".split_once('='), Some(("cfg", "foo=bar")));

1.52.0

#### pub fn rsplit_once<'a, P>(&'a self, delimiter: P) -> Option<(&'a str, &'a str)>where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

Splits the string on the last occurrence of the specified delimiter and returns prefix before delimiter and suffix after delimiter.

##### Examples

    assert_eq!("cfg".rsplit_once('='), None);
    assert_eq!("cfg=foo".rsplit_once('='), Some(("cfg", "foo")));
    assert_eq!("cfg=foo=bar".rsplit_once('='), Some(("cfg=foo", "bar")));

1.2.0

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

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

The pattern can be a `&str`, `char`, a slice of `char`s, or a function or 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, e.g., `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

    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"]);

1.2.0

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

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

The pattern can be a `&str`, `char`, a slice of `char`s, or a function or 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

    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"]);

1.5.0

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

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`, a slice of `char`s, or a function or 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, e.g., `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

    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`

1.5.0

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

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`, a slice of `char`s, or a function or 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

    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`

1.0.0

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

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`, which includes newlines.

##### Examples

    let s = "\n Hello\tworld\t\n";

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

1.30.0

#### pub fn trim_start(&self) -> &str

Returns a string slice with leading whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property `White_Space`, which includes newlines.

##### Text directionality

A string is a sequence of bytes. `start` in this context means the first position of that byte string; for a left-to-right language like English or Russian, this will be left side, and for right-to-left languages like Arabic or Hebrew, this will be the right side.

##### Examples

Basic usage:

    let s = "\n Hello\tworld\t\n";
    assert_eq!("Hello\tworld\t\n", s.trim_start());

Directionality:

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

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

1.30.0

#### pub fn trim_end(&self) -> &str

Returns a string slice with trailing whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property `White_Space`, which includes newlines.

##### Text directionality

A string is a sequence of bytes. `end` in this context means the last position of that byte string; for a left-to-right language like English or Russian, this will be right side, and for right-to-left languages like Arabic or Hebrew, this will be the left side.

##### Examples

Basic usage:

    let s = "\n Hello\tworld\t\n";
    assert_eq!("\n Hello\tworld", s.trim_end());

Directionality:

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

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

1.0.0

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

👎Deprecated since 1.33.0: superseded by `trim_start`

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());

Directionality:

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

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

1.0.0

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

👎Deprecated since 1.33.0: superseded by `trim_end`

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());

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());

1.0.0

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

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

The pattern can be a `char`, a slice of `char`s, or a function or 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");

A more complex pattern, using a closure:

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

1.30.0

#### pub fn trim_start_matches<'a, P>(&'a self, pat: P) -> &'a strwhere P: Pattern<'a>,

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

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

##### Text directionality

A string is a sequence of bytes. `start` in this context means the first position of that byte string; for a left-to-right language like English or Russian, this will be left side, and for right-to-left languages like Arabic or Hebrew, this will be the right side.

##### Examples

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

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

1.45.0

#### pub fn strip_prefix<'a, P>(&'a self, prefix: P) -> Option<&'a str>where P: Pattern<'a>,

Returns a string slice with the prefix removed.

If the string starts with the pattern `prefix`, returns substring after the prefix, wrapped in `Some`. Unlike `trim_start_matches`, this method removes the prefix exactly once.

If the string does not start with `prefix`, returns `None`.

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

##### Examples

    assert_eq!("foo:bar".strip_prefix("foo:"), Some("bar"));
    assert_eq!("foo:bar".strip_prefix("bar"), None);
    assert_eq!("foofoo".strip_prefix("foo"), Some("foo"));

1.45.0

#### pub fn strip_suffix<'a, P>(&'a self, suffix: P) -> Option<&'a str>where P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

Returns a string slice with the suffix removed.

If the string ends with the pattern `suffix`, returns the substring before the suffix, wrapped in `Some`. Unlike `trim_end_matches`, this method removes the suffix exactly once.

If the string does not end with `suffix`, returns `None`.

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

##### Examples

    assert_eq!("bar:foo".strip_suffix(":foo"), Some("bar"));
    assert_eq!("bar:foo".strip_suffix("bar"), None);
    assert_eq!("foofoo".strip_suffix("foo"), Some("foo"));

1.30.0

#### pub fn trim_end_matches<'a, P>(&'a self, pat: P) -> &'a strwhere P: Pattern<'a>, <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

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

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

##### Text directionality

A string is a sequence of bytes. `end` in this context means the last position of that byte string; for a left-to-right language like English or Russian, this will be right side, and for right-to-left languages like Arabic or Hebrew, this will be the left side.

##### Examples

Simple patterns:

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

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

A more complex pattern, using a closure:

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

1.0.0

#### pub fn trim_left_matches<'a, P>(&'a self, pat: P) -> &'a strwhere P: Pattern<'a>,

👎Deprecated since 1.33.0: superseded by `trim_start_matches`

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

The pattern can be a `&str`, `char`, a slice of `char`s, or a function or 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

    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");

1.0.0

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

👎Deprecated since 1.33.0: superseded by `trim_end_matches`

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

The pattern can be a `&str`, `char`, a slice of `char`s, or a function or 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");

A more complex pattern, using a closure:

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

1.0.0

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

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 into 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);

Using the ‘turbofish’ instead of annotating `four`:

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

    assert_eq!(Ok(4), four);

Failing to parse:

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

    assert!(nope.is_err());

1.23.0

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

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());

#### pub fn as_ascii(&self) -> Option<&[AsciiChar]>

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

If this string slice `is_ascii`, returns it as a slice of ASCII characters, otherwise returns `None`.

1.23.0

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

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"));

1.23.0

#### pub fn make_ascii_uppercase(&mut self)

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()`.

##### Examples

    let mut s = String::from("Grüße, Jürgen ❤");

    s.make_ascii_uppercase();

    assert_eq!("GRüßE, JüRGEN ❤", s);

1.23.0

#### pub fn make_ascii_lowercase(&mut self)

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()`.

##### Examples

    let mut s = String::from("GRÜßE, JÜRGEN ❤");

    s.make_ascii_lowercase();

    assert_eq!("grÜße, jÜrgen ❤", s);

1.34.0

#### pub fn escape_debug(&self) -> EscapeDebug<'_>

Return an iterator that escapes each char in `self` with [`char::escape_debug`].

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

##### Examples

As an iterator:

    for c in "❤\n!".escape_debug() {
        print!("{c}");
    }
    println!();

Using `println!` directly:

    println!("{}", "❤\n!".escape_debug());

Both are equivalent to:

    println!("❤\\n!");

Using `to_string`:

    assert_eq!("❤\n!".escape_debug().to_string(), "❤\\n!");

1.34.0

#### pub fn escape_default(&self) -> EscapeDefault<'_>

Return an iterator that escapes each char in `self` with [`char::escape_default`].

##### Examples

As an iterator:

    for c in "❤\n!".escape_default() {
        print!("{c}");
    }
    println!();

Using `println!` directly:

    println!("{}", "❤\n!".escape_default());

Both are equivalent to:

    println!("\\u{{2764}}\\n!");

Using `to_string`:

    assert_eq!("❤\n!".escape_default().to_string(), "\\u{2764}\\n!");

1.34.0

#### pub fn escape_unicode(&self) -> EscapeUnicode<'_>

Return an iterator that escapes each char in `self` with [`char::escape_unicode`].

##### Examples

As an iterator:

    for c in "❤\n!".escape_unicode() {
        print!("{c}");
    }
    println!();

Using `println!` directly:

    println!("{}", "❤\n!".escape_unicode());

Both are equivalent to:

    println!("\\u{{2764}}\\u{{a}}\\u{{21}}");

Using `to_string`:

    assert_eq!("❤\n!".escape_unicode().to_string(), "\\u{2764}\\u{a}\\u{21}");

## Trait Implementations§

source§

### impl<const N: usize> AsRef<[u8]> for String<N>

source§

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

Converts this type into a shared reference of the (usually inferred) input type.
source§

### impl<const N: usize> AsRef<str> for String<N>

source§

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

Converts this type into a shared reference of the (usually inferred) input type.
source§

### impl<const N: usize> Clone for String<N>

source§

#### fn clone(&self) -> String<N>

Returns a copy of the value. Read more
1.0.0§

#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
source§

### impl<const N: usize> Debug for String<N>

source§

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

Formats the value using the given formatter. Read more
source§

### impl<const N: usize> Default for String<N>

source§

#### fn default() -> String<N>

Returns the “default value” for a type. Read more
source§

### impl<const N: usize> Deref for String<N>

§

#### type Target = str

The resulting type after dereferencing.
source§

#### fn deref(&self) -> &str

Dereferences the value.
source§

### impl<const N: usize> DerefMut for String<N>

source§

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

Mutably dereferences the value.
source§

### impl<const N: usize> Display for String<N>

source§

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

Formats the value using the given formatter. Read more
source§

### impl<const N: usize> DrawableString for String<N>

source§

#### fn draw(self)

source§

### impl<'a, const N: usize> From<&'a str> for String<N>

source§

#### fn from(s: &'a str) -> String<N>

Converts to this type from the input type.
source§

### impl<const N: usize> From<i16> for String<N>

source§

#### fn from(s: i16) -> String<N>

Converts to this type from the input type.
source§

### impl<const N: usize> From<i32> for String<N>

source§

#### fn from(s: i32) -> String<N>

Converts to this type from the input type.
source§

### impl<const N: usize> From<i64> for String<N>

source§

#### fn from(s: i64) -> String<N>

Converts to this type from the input type.
source§

### impl<const N: usize> From<i8> for String<N>

source§

#### fn from(s: i8) -> String<N>

Converts to this type from the input type.
source§

### impl<const N: usize> From<u16> for String<N>

source§

#### fn from(s: u16) -> String<N>

Converts to this type from the input type.
source§

### impl<const N: usize> From<u32> for String<N>

source§

#### fn from(s: u32) -> String<N>

Converts to this type from the input type.
source§

### impl<const N: usize> From<u64> for String<N>

source§

#### fn from(s: u64) -> String<N>

Converts to this type from the input type.
source§

### impl<const N: usize> From<u8> for String<N>

source§

#### fn from(s: u8) -> String<N>

Converts to this type from the input type.
source§

### impl<'a, const N: usize> FromIterator<&'a char> for String<N>

source§

#### fn from_iter<T>(iter: T) -> String<N>where T: IntoIterator<Item = &'a char>,

Creates a value from an iterator. Read more
source§

### impl<'a, const N: usize> FromIterator<&'a str> for String<N>

source§

#### fn from_iter<T>(iter: T) -> String<N>where T: IntoIterator<Item = &'a str>,

Creates a value from an iterator. Read more
source§

### impl<const N: usize> FromIterator<char> for String<N>

source§

#### fn from_iter<T>(iter: T) -> String<N>where T: IntoIterator<Item = char>,

Creates a value from an iterator. Read more
source§

### impl<const N: usize> FromStr for String<N>

§

#### type Err = ()

The associated error which can be returned from parsing.
source§

#### fn from_str(s: &str) -> Result<String<N>, <String<N> as FromStr>::Err>

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

### impl<const N: usize> Hash for String<N>

source§

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

Feeds this value into the given [`Hasher`]. Read more
1.3.0§

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

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

### impl<const N: usize> Hash for String<N>

source§

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

Feeds this value into the given `Hasher`.
source§

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

Feeds a slice of this type into the given `Hasher`.
source§

### impl<const N: usize> Ord for String<N>

source§

#### fn cmp(&self, other: &String<N>) -> Ordering

This method returns an [`Ordering`] between `self` and `other`. Read more
1.21.0§

#### fn max(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the maximum of two values. Read more
1.21.0§

#### fn min(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the minimum of two values. Read more
1.50.0§

#### fn clamp(self, min: Self, max: Self) -> Selfwhere Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval. Read more
source§

### impl<const N: usize> PartialEq<&str> for String<N>

source§

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

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

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

This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

### impl<const N: usize> PartialEq<String<N>> for &str

source§

#### fn eq(&self, other: &String<N>) -> bool

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

#### fn ne(&self, other: &String<N>) -> bool

This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

### impl<const N: usize> PartialEq<String<N>> for str

source§

#### fn eq(&self, other: &String<N>) -> bool

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

#### fn ne(&self, other: &String<N>) -> bool

This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

### impl<const N1: usize, const N2: usize> PartialEq<String<N2>> for String<N1>

source§

#### fn eq(&self, rhs: &String<N2>) -> bool

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

#### fn ne(&self, rhs: &String<N2>) -> bool

This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

### impl<const N: usize> PartialEq<str> for String<N>

source§

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

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

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

This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

### impl<const N1: usize, const N2: usize> PartialOrd<String<N2>> for String<N1>

source§

#### fn partial_cmp(&self, other: &String<N2>) -> Option<Ordering>

This method returns an ordering between `self` and `other` values if one exists. Read more
1.0.0§

#### fn lt(&self, other: &Rhs) -> bool

This method tests less than (for `self` and `other`) and is used by the `<` operator. Read more
1.0.0§

#### fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more
1.0.0§

#### fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more
1.0.0§

#### fn ge(&self, other: &Rhs) -> bool

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

### impl<const N: usize> Printable for String<N>

§

#### type Parameters = ()

source§

#### fn print_2(self, _params: Self::Parameters)

source§

#### fn default_parameters() -> Self::Parameters

source§

#### fn print(self)

source§

### impl<const N: usize> Serialprintable for String<N>

§

#### type Parameters = ()

source§

#### fn print_2(self, _params: Self::Parameters)

source§

#### fn default_parameters() -> Self::Parameters

source§

#### fn print(self)

source§

### impl<const N: usize> Serialprintlnable for String<N>

§

#### type Parameters = ()

source§

#### fn println_2(self, _params: Self::Parameters)

source§

#### fn default_parameters() -> Self::Parameters

source§

#### fn println(self)

source§

### impl<const N: usize> Write for String<N>

source§

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

Writes a string slice into this writer, returning whether the write succeeded. Read more
source§

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

Writes a [`char`] into this writer, returning whether the write succeeded. Read more
1.0.0§

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

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

### impl<const N: usize> Eq for String<N>

## Auto Trait Implementations§

§

### impl<const N: usize> RefUnwindSafe for String<N>

§

### impl<const N: usize> Send for String<N>

§

### impl<const N: usize> Sync for String<N>

§

### impl<const N: usize> Unpin for String<N>

§

### impl<const N: usize> UnwindSafe for String<N>

## Blanket Implementations§

§

### impl<T> Any for Twhere T: 'static + ?Sized,

§

#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
§

### impl<T> Borrow<T> for Twhere T: ?Sized,

§

#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
§

### impl<T> BorrowMut<T> for Twhere T: ?Sized,

§

#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
§

### impl<T> From<T> for T

§

#### fn from(t: T) -> T

Returns the argument unchanged.

§

### impl<T, U> Into<U> for Twhere U: From<T>,

§

#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `[From]<T> for U` chooses to do.

§

### impl<T, U> TryFrom<U> for Twhere U: Into<T>,

§

#### type Error = Infallible

The type returned in the event of a conversion error.
§

#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
§

### impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

§

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
§

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.