Struct rafx::base::trust_cell::RefMut
source · pub struct RefMut<'a, T>where
T: 'a + ?Sized,{ /* private fields */ }
Expand description
A mutable reference to data in a TrustCell
.
Access the value via std::ops::DerefMut
(e.g. *val
)
Implementations§
source§impl<'a, T> RefMut<'a, T>where
T: ?Sized,
impl<'a, T> RefMut<'a, T>where
T: ?Sized,
sourcepub fn map<U, F>(self, f: F) -> RefMut<'a, U>
pub fn map<U, F>(self, f: F) -> RefMut<'a, U>
Makes a new RefMut
for a component of the borrowed data which
preserves the existing borrow.
The TrustCell
is already mutably borrowed, so this cannot fail.
This is an associated function that needs to be used as
RefMut::map(...)
. A method would interfere with methods of the
same name on the contents of a RefMut
used through DerefMut
.
Further this preserves the borrow of the value and hence does the
proper cleanup when it’s dropped.
§Examples
This can also be used to avoid pointer indirection when a boxed item is
stored in the TrustCell
.
use rafx_base::trust_cell::{RefMut, TrustCell};
let cb = TrustCell::new(Box::new(5));
// Borrowing the cell causes the `RefMut` to store a reference to the `Box`, which is a
// pointer to the value on the heap, and not a reference directly to the value.
let boxed_ref: RefMut<'_, Box<usize>> = cb.borrow_mut();
assert_eq!(**boxed_ref, 5); // Notice the double deref to get the actual value.
// By using `map` we can let `RefMut` store a reference directly to the value on the heap.
let pure_ref: RefMut<'_, usize> = RefMut::map(boxed_ref, Box::as_mut);
assert_eq!(*pure_ref, 5);
We can also use map
to get a reference to a sub-part of the borrowed
value.
let c = TrustCell::new((5, 'b'));
let b1: RefMut<'_, (u32, char)> = c.borrow_mut();
let b2: RefMut<'_, u32> = RefMut::map(b1, |t| &mut t.0);
assert_eq!(*b2, 5);
Trait Implementations§
Auto Trait Implementations§
impl<'a, T: ?Sized> RefUnwindSafe for RefMut<'a, T>where
T: RefUnwindSafe,
impl<'a, T: ?Sized> Send for RefMut<'a, T>where
T: Send,
impl<'a, T: ?Sized> Sync for RefMut<'a, T>where
T: Sync,
impl<'a, T: ?Sized> Unpin for RefMut<'a, T>
impl<'a, T> !UnwindSafe for RefMut<'a, T>
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
§impl<T> Downcast for Twhere
T: Any,
impl<T> Downcast for Twhere
T: Any,
§fn into_any(self: Box<T>) -> Box<dyn Any>
fn into_any(self: Box<T>) -> Box<dyn Any>
Convert
Box<dyn Trait>
(where Trait: Downcast
) to Box<dyn Any>
. Box<dyn Any>
can
then be further downcast
into Box<ConcreteType>
where ConcreteType
implements Trait
.§fn into_any_rc(self: Rc<T>) -> Rc<dyn Any>
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any>
Convert
Rc<Trait>
(where Trait: Downcast
) to Rc<Any>
. Rc<Any>
can then be
further downcast
into Rc<ConcreteType>
where ConcreteType
implements Trait
.§fn as_any(&self) -> &(dyn Any + 'static)
fn as_any(&self) -> &(dyn Any + 'static)
Convert
&Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &Any
’s vtable from &Trait
’s.§fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
Convert
&mut Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &mut Any
’s vtable from &mut Trait
’s.