collections::borrow::Borrow

Trait collections::borrow::Borrow

pub trait Borrow<Borrowed> where    Borrowed: ?Sized, {
    fn borrow(&self) -> &Borrowed;
}

A trait for borrowing data.

In general, there may be several ways to "borrow" a piece of data. The typical ways of borrowing a type T are &T (a shared borrow) and &mut T (a mutable borrow). But types like Vec<T> provide additional kinds of borrows: the borrowed slices &[T] and &mut [T].

When writing generic code, it is often desirable to abstract over all ways of borrowing data from a given type. That is the role of the Borrow trait: if T: Borrow<U>, then &U can be borrowed from &T. A given type can be borrowed as multiple different types. In particular, Vec<T>: Borrow<Vec<T>> and Vec<T>: Borrow<[T]>.

If you are implementing Borrow and both Self and Borrowed implement Hash, Eq, and/or Ord, they must produce the same result.

Borrow is very similar to, but different than, AsRef. See the book for more.

Required Methods

use std::borrow::Borrow;

fn check<T: Borrow<str>>(s: T) {
    assert_eq!("Hello", s.borrow());
}

let s = "Hello".to_string();

check(s);

let s = "Hello";

check(s);

Implementors

• impl<T> Borrow<T> for T where
    T: ?Sized, 
• impl<'a, T> Borrow<T> for &'a T where
    T: ?Sized, 
• impl<'a, T> Borrow<T> for &'a mut T where
    T: ?Sized, 
• impl<T> Borrow<[T]> for [T; 0]
• impl<T> Borrow<[T]> for [T; 1]
• impl<T> Borrow<[T]> for [T; 2]
• impl<T> Borrow<[T]> for [T; 3]
• impl<T> Borrow<[T]> for [T; 4]
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• impl<T> Borrow<[T]> for [T; 6]
• impl<T> Borrow<[T]> for [T; 7]
• impl<T> Borrow<[T]> for [T; 8]
• impl<T> Borrow<[T]> for [T; 9]
• impl<T> Borrow<[T]> for [T; 10]
• impl<T> Borrow<[T]> for [T; 11]
• impl<T> Borrow<[T]> for [T; 12]
• impl<T> Borrow<[T]> for [T; 13]
• impl<T> Borrow<[T]> for [T; 14]
• impl<T> Borrow<[T]> for [T; 15]
• impl<T> Borrow<[T]> for [T; 16]
• impl<T> Borrow<[T]> for [T; 17]
• impl<T> Borrow<[T]> for [T; 18]
• impl<T> Borrow<[T]> for [T; 19]
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• impl<T> Borrow<[T]> for [T; 21]
• impl<T> Borrow<[T]> for [T; 22]
• impl<T> Borrow<[T]> for [T; 23]
• impl<T> Borrow<[T]> for [T; 24]
• impl<T> Borrow<[T]> for [T; 25]
• impl<T> Borrow<[T]> for [T; 26]
• impl<T> Borrow<[T]> for [T; 27]
• impl<T> Borrow<[T]> for [T; 28]
• impl<T> Borrow<[T]> for [T; 29]
• impl<T> Borrow<[T]> for [T; 30]
• impl<T> Borrow<[T]> for [T; 31]
• impl<T> Borrow<[T]> for [T; 32]
• impl<T> Borrow<T> for Box<T> where
    T: ?Sized, 
• impl<T> Borrow<T> for Arc<T> where
    T: ?Sized, 
• impl<T> Borrow<T> for Rc<T> where
    T: ?Sized, 
• impl<'a, B: ?Sized> Borrow<B> for Cow<'a, B> where
    B: ToOwned,
    <B as ToOwned>::Owned: 'a, 
• impl<T> Borrow<[T]> for Vec<T>
• impl Borrow<str> for String