Trait core::convert::AsRef 1.0.0
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[src]
pub trait AsRef<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
AsRefwhen goal is to simply convert into a reference - Use
Borrowwhen goal is related to writing code that is agnostic to the type of borrow and if is 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
AsRefauto-dereferences if the inner type is a reference or a mutable reference (e.g.:foo.as_ref()will work the same iffoohas type&mut Fooor&&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
fn as_ref(&self) -> &T
Performs the conversion.
Implementors
impl<'a, T: ?Sized, U: ?Sized> AsRef<U> for &'a T where
T: AsRef<U>,impl<'a, T: ?Sized, U: ?Sized> AsRef<U> for &'a mut T where
T: AsRef<U>,impl<T> AsRef<[T]> for [T]impl AsRef<str> for strimpl<T> AsRef<[T]> for [T; 0]impl<T> AsRef<[T]> for [T; 1]impl<T> AsRef<[T]> for [T; 2]impl<T> AsRef<[T]> for [T; 3]impl<T> AsRef<[T]> for [T; 4]impl<T> AsRef<[T]> for [T; 5]impl<T> AsRef<[T]> for [T; 6]impl<T> AsRef<[T]> for [T; 7]impl<T> AsRef<[T]> for [T; 8]impl<T> AsRef<[T]> for [T; 9]impl<T> AsRef<[T]> for [T; 10]impl<T> AsRef<[T]> for [T; 11]impl<T> AsRef<[T]> for [T; 12]impl<T> AsRef<[T]> for [T; 13]impl<T> AsRef<[T]> for [T; 14]impl<T> AsRef<[T]> for [T; 15]impl<T> AsRef<[T]> for [T; 16]impl<T> AsRef<[T]> for [T; 17]impl<T> AsRef<[T]> for [T; 18]impl<T> AsRef<[T]> for [T; 19]impl<T> AsRef<[T]> for [T; 20]impl<T> AsRef<[T]> for [T; 21]impl<T> AsRef<[T]> for [T; 22]impl<T> AsRef<[T]> for [T; 23]impl<T> AsRef<[T]> for [T; 24]impl<T> AsRef<[T]> for [T; 25]impl<T> AsRef<[T]> for [T; 26]impl<T> AsRef<[T]> for [T; 27]impl<T> AsRef<[T]> for [T; 28]impl<T> AsRef<[T]> for [T; 29]impl<T> AsRef<[T]> for [T; 30]impl<T> AsRef<[T]> for [T; 31]impl<T> AsRef<[T]> for [T; 32]impl<'a, T> AsRef<[T]> for Iter<'a, T>impl AsRef<[u8]> for str