Expand description
Used to do a cheap mutable-to-mutable reference conversion.
This trait is similar to AsRef
but used for converting between mutable
references. If you need to do a costly conversion it is better to
implement From
with type &mut T
or write a custom function.
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
AsMut
auto-dereferences if the inner type is a mutable reference (e.g.:foo.as_mut()
will work the same iffoo
has type&mut Foo
or&mut &mut Foo
)
Examples
Using AsMut
as trait bound for a generic function we can accept all mutable references
that can be converted to type &mut T
. Because Box<T>
implements AsMut<T>
we can
write a function add_one
that takes all arguments that can be converted to &mut u64
.
Because Box<T>
implements AsMut<T>
, add_one
accepts arguments of type
&mut Box<u64>
as well:
fn add_one<T: AsMut<u64>>(num: &mut T) {
*num.as_mut() += 1;
}
let mut boxed_num = Box::new(0);
add_one(&mut boxed_num);
assert_eq!(*boxed_num, 1);
Run