1.0.0[−][src]Trait std::convert::AsRef
Used to do a cheap reference-to-reference conversion.
This trait is similar to AsMut which is used for converting between mutable references.
If you need to do a costly conversion it is better to implement From with type
&T or write a custom function.
AsRef has the same signature as Borrow, but Borrow is different in few aspects:
- Unlike
AsRef,Borrowhas a blanket impl for anyT, and can be used to accept either a reference or a value. Borrowalso requires thatHash,EqandOrdfor borrowed value are equivalent to those of the owned value. For this reason, if you want to borrow only a single field of a struct you can implementAsRef, but notBorrow.
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
By using trait bounds we can accept arguments of different types as long as they can be
converted to the specified type T.
For example: By creating a generic function that takes an AsRef<str> we express that we
want to accept all references that can be converted to [&str] as an argument.
Since both String and [&str] implement AsRef<str> we can accept both as input argument.
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ⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut WPerforms the conversion.
Implementors
impl AsRef<[u8]> for str[src]
impl AsRef<[u8]> for String[src]
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<'_> AsRef<OsStr> for Component<'_>[src]
impl<'_> AsRef<OsStr> for Components<'_>[src]
impl<'_> AsRef<OsStr> for std::path::Iter<'_>[src]
impl<'_> AsRef<Path> for Cow<'_, OsStr>[src]
impl<'_> AsRef<Path> for Component<'_>[src]
impl<'_> AsRef<Path> for Components<'_>[src]
impl<'_> AsRef<Path> for std::path::Iter<'_>[src]
impl<'_, T> AsRef<[T]> for std::slice::Iter<'_, T>[src]
impl<'_, T> AsRef<T> for Cow<'_, T> where
T: ToOwned + ?Sized, [src]
T: ToOwned + ?Sized,
fn as_ref(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W[src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut Wimpl<'_, T, U> AsRef<U> for &'_ T where
T: AsRef<U> + ?Sized,
U: ?Sized, [src]
T: AsRef<U> + ?Sized,
U: ?Sized,
fn as_ref(&self) -> &UⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W[src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut Wimpl<'_, T, U> AsRef<U> for &'_ mut T where
T: AsRef<U> + ?Sized,
U: ?Sized, [src]
T: AsRef<U> + ?Sized,
U: ?Sized,
fn as_ref(&self) -> &UⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W[src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut Wimpl<'a, T> AsRef<[T]> for Drain<'a, T>[src]
impl<T> AsRef<[T]> for [T][src]
impl<T> AsRef<[T]> for IntoIter<T>[src]
impl<T> AsRef<[T]> for Vec<T>[src]
impl<T> AsRef<Vec<T>> for Vec<T>[src]
impl<T> AsRef<T> for Box<T> where
T: ?Sized, [src]
T: ?Sized,
fn as_ref(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W[src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut Wimpl<T> AsRef<T> for Rc<T> where
T: ?Sized, [src]
T: ?Sized,
fn as_ref(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W[src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut Wimpl<T> AsRef<T> for Arc<T> where
T: ?Sized, [src]
T: ?Sized,
fn as_ref(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W[src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W