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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);

Required Methods

ⓘImportant traits for &'a mut I
impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'a, R: Read + ?Sized> Read for &'a mut R
impl<'a, W: Write + ?Sized> Write for &'a mut W

Performs the conversion.

Implementors

impl AsRef<[u8]> for str [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl AsRef<[u8]> for String [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl AsRef<str> for str [src]

impl AsRef<str> for String [src]

impl AsRef<CStr> for CStr [src]

impl AsRef<CStr> for CString [src]

impl AsRef<OsStr> for str [src]

impl AsRef<OsStr> for OsStr [src]

impl AsRef<OsStr> for OsString [src]

impl AsRef<OsStr> for Path [src]

impl AsRef<OsStr> for PathBuf [src]

impl AsRef<OsStr> for String [src]

impl AsRef<Path> for str [src]

impl AsRef<Path> for OsStr [src]

impl AsRef<Path> for OsString [src]

impl AsRef<Path> for Path [src]

impl AsRef<Path> for PathBuf [src]

impl AsRef<Path> for String [src]

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

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

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

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

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

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

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

impl<'a, T> AsRef<[T]> for std::slice::Iter<'a, T> [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

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

ⓘImportant traits for &'a mut I
impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'a, R: Read + ?Sized> Read for &'a mut R
impl<'a, W: Write + ?Sized> Write for &'a mut W

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

ⓘImportant traits for &'a mut I
impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'a, R: Read + ?Sized> Read for &'a mut R
impl<'a, W: Write + ?Sized> Write for &'a mut W

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

ⓘImportant traits for &'a mut I
impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'a, R: Read + ?Sized> Read for &'a mut R
impl<'a, W: Write + ?Sized> Write for &'a mut W

impl<T> AsRef<[T]> for [T; 0] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 1] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 2] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 3] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 4] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 5] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 6] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 7] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 8] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 9] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 10] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 11] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 12] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 13] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 14] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 15] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 16] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 17] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 18] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 19] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 20] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 21] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 22] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 23] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 24] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 25] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 26] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 27] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 28] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 29] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 30] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 31] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T; 32] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

impl<T> AsRef<[T]> for [T] [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

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

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]

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

ⓘImportant traits for Vec<u8>
impl Write for Vec<u8>

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

ⓘImportant traits for &'a mut I
impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'a, R: Read + ?Sized> Read for &'a mut R
impl<'a, W: Write + ?Sized> Write for &'a mut W

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

ⓘImportant traits for &'a mut I
impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'a, R: Read + ?Sized> Read for &'a mut R
impl<'a, W: Write + ?Sized> Write for &'a mut W

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

ⓘImportant traits for &'a mut I
impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'a, R: Read + ?Sized> Read for &'a mut R
impl<'a, W: Write + ?Sized> Write for &'a mut W

© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/convert/trait.AsRef.html