Struct rafx::base::trust_cell::Ref
source · pub struct Ref<'a, T>where
T: 'a + ?Sized,{
pub value: &'a T,
/* private fields */
}
Expand description
An immutable reference to data in a TrustCell
.
Access the value via std::ops::Deref
(e.g. *val
)
Fields§
§value: &'a T
Implementations§
source§impl<'a, T> Ref<'a, T>where
T: ?Sized,
impl<'a, T> Ref<'a, T>where
T: ?Sized,
sourcepub fn map<U, F>(self, f: F) -> Ref<'a, U>
pub fn map<U, F>(self, f: F) -> Ref<'a, U>
Makes a new Ref
for a component of the borrowed data which preserves
the existing borrow.
The TrustCell
is already immutably borrowed, so this cannot fail.
This is an associated function that needs to be used as Ref::map(...)
.
A method would interfere with methods of the same name on the contents
of a Ref
used through Deref
. Further this preserves the borrow of
the value and hence does the proper cleanup when it’s dropped.
§Examples
This can be used to avoid pointer indirection when a boxed item is
stored in the TrustCell
.
use rafx_base::trust_cell::{Ref, TrustCell};
let cb = TrustCell::new(Box::new(5));
// Borrowing the cell causes the `Ref` to store a reference to the `Box`, which is a
// pointer to the value on the heap, not the actual value.
let boxed_ref: Ref<'_, Box<usize>> = cb.borrow();
assert_eq!(**boxed_ref, 5); // Notice the double deref to get the actual value.
// By using `map` we can let `Ref` store a reference directly to the value on the heap.
let pure_ref: Ref<'_, usize> = Ref::map(boxed_ref, Box::as_ref);
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: Ref<'_, (u32, char)> = c.borrow();
let b2: Ref<'_, u32> = Ref::map(b1, |t| &t.0);
assert_eq!(*b2, 5);
Trait Implementations§
Auto Trait Implementations§
impl<'a, T: ?Sized> RefUnwindSafe for Ref<'a, T>where
T: RefUnwindSafe,
impl<'a, T: ?Sized> Send for Ref<'a, T>where
T: Sync,
impl<'a, T: ?Sized> Sync for Ref<'a, T>where
T: Sync,
impl<'a, T: ?Sized> Unpin for Ref<'a, T>
impl<'a, T: ?Sized> UnwindSafe for Ref<'a, T>where
T: RefUnwindSafe,
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.