Trait std::convert::AsRef1.0.0 [] [src]

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:

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


Both String and &str implement AsRef<str>:

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

let s = "hello";

let s = "hello".to_string();

Required Methods

Performs the conversion.