std::convert::AsRef - Rust
Description: API documentation for the Rust `AsRef` trait in crate `std`.
Keywords: rust, rustlang, rust-lang, AsRef

# 1.0.0[−][src]Trait std::convert::AsRef

    pub trait AsRef<T> where
        T: ?Sized, {
        fn as_ref(&self) -> &T;
    }

A cheap reference-to-reference conversion. Used to convert a value to a reference value within generic code.

`AsRef` is very similar to, but serves a slightly different purpose than, `Borrow`.

`AsRef` is to be used when wishing to convert to a reference of another type. `Borrow` is more related to the notion of taking the reference. It is useful when wishing to abstract over the type of reference (`&T`, `&mut T`) or allow both the referenced and owned type to be treated in the same manner.

The key difference between the two traits is the intention:

- Use `AsRef` when the goal is to simply convert into a reference
- Use `Borrow` when the goal is related to writing code that is agnostic to the type of borrow and whether it is a reference or value

See the book for a more detailed comparison.

Note: this trait must not fail. If the conversion can fail, use a dedicated method which returns an `Option<T>` or a `Result<T, E>`.

# Generic Implementations

- `AsRef` auto-dereferences if the inner type is a reference or a mutable reference (e.g.: `foo.as_ref()` will work the same if `foo` has type `&mut Foo` or `&&mut Foo`)

# Examples

Both `String` and `&str` implement `AsRef<str>`:

    fn is_hello<T: AsRef<str>>(s: T) {
       assert_eq!("hello", s.as_ref());
    }

    let s = "hello";
    is_hello(s);

    let s = "hello".to_string();
    is_hello(s);Run

## Required methods

###
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn as_ref(&self) -> &T`

Performs the conversion.

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## Implementors

### `impl AsRef<[u8]> for str`[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]

### `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]

### `impl AsRef<str> for str`[src]

#### `fn as_ref(&self) -> &str`[src]

### `impl AsRef<str> for String`[src]

#### `fn as_ref(&self) -> &str`[src]

### `impl AsRef<CStr> for CStr`[src]

#### `fn as_ref(&self) -> &CStr`[src]

### `impl AsRef<CStr> for CString`[src]

#### `fn as_ref(&self) -> &CStr`[src]

### `impl AsRef<OsStr> for str`[src]

#### `fn as_ref(&self) -> &OsStr`[src]

### `impl AsRef<OsStr> for OsStr`[src]

#### `fn as_ref(&self) -> &OsStr`[src]

### `impl AsRef<OsStr> for OsString`[src]

#### `fn as_ref(&self) -> &OsStr`[src]

### `impl AsRef<OsStr> for Path`[src]

#### `fn as_ref(&self) -> &OsStr`[src]

### `impl AsRef<OsStr> for PathBuf`[src]

#### `fn as_ref(&self) -> &OsStr`[src]

### `impl AsRef<OsStr> for String`[src]

#### `fn as_ref(&self) -> &OsStr`[src]

### `impl AsRef<Path> for str`[src]

#### `fn as_ref(&self) -> &Path`[src]

### `impl AsRef<Path> for OsStr`[src]

#### `fn as_ref(&self) -> &Path`[src]

### `impl AsRef<Path> for OsString`[src]

#### `fn as_ref(&self) -> &Path`[src]

### `impl AsRef<Path> for Path`[src]

#### `fn as_ref(&self) -> &Path`[src]

### `impl AsRef<Path> for PathBuf`[src]

#### `fn as_ref(&self) -> &Path`[src]

### `impl AsRef<Path> for String`[src]

#### `fn as_ref(&self) -> &Path`[src]

### `impl<'_, T> AsRef<[T]> for std::slice::Iter<'_, T>`[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) -> &[T]`[src]

### `impl<'_, T, U> AsRef<U> for &'_ T where
T: AsRef<U> + ?Sized,
U: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn as_ref(&self) -> &U`[src]

### `impl<'_, T, U> AsRef<U> for &'_ mut T where
T: AsRef<U> + ?Sized,
U: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn as_ref(&self) -> &U`[src]

### `impl<'a> AsRef<OsStr> for Component<'a>`[src]

#### `fn as_ref(&self) -> &OsStr`[src]

### `impl<'a> AsRef<OsStr> for Components<'a>`[src]

#### `fn as_ref(&self) -> &OsStr`[src]

### `impl<'a> AsRef<OsStr> for std::path::Iter<'a>`[src]

#### `fn as_ref(&self) -> &OsStr`[src]

### `impl<'a> AsRef<Path> for Cow<'a, OsStr>`[src]

#### `fn as_ref(&self) -> &Path`[src]

### `impl<'a> AsRef<Path> for Component<'a>`[src]

#### `fn as_ref(&self) -> &Path`[src]

### `impl<'a> AsRef<Path> for Components<'a>`[src]

#### `fn as_ref(&self) -> &Path`[src]

### `impl<'a> AsRef<Path> for std::path::Iter<'a>`[src]

#### `fn as_ref(&self) -> &Path`[src]

### `impl<'a, T> AsRef<T> for Cow<'a, T> where
T: ToOwned + ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn as_ref(&self) -> &T`[src]

### `impl<T> AsRef<[T]> for [T; 0]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 1]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 2]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 3]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 4]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 5]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 6]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 7]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 8]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 9]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 10]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 11]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 12]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 13]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 14]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 15]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 16]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 17]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 18]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 19]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 20]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 21]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 22]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 23]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 24]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 25]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 26]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 27]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 28]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 29]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 30]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 31]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T; 32]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for [T]`[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) -> &[T]`[src]

### `impl<T> AsRef<[T]> for Vec<T>`[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) -> &[T]`[src]

### `impl<T> AsRef<Vec<T>> for Vec<T>`[src]

####
ⓘImportant traits for Vec<u8>

### Important traits for Vec<u8>

`impl Write for Vec<u8>`
`fn as_ref(&self) -> &Vec<T>`[src]

### `impl<T> AsRef<T> for Box<T> where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn as_ref(&self) -> &T`[src]

### `impl<T> AsRef<T> for Rc<T> where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn as_ref(&self) -> &T`[src]

### `impl<T> AsRef<T> for Arc<T> where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn as_ref(&self) -> &T`[src]

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