pub struct Ref<'b, T: ?Sized + 'b> { /* private fields */ }
Expand description
Wraps a borrowed reference to a value in a RefCell
box.
A wrapper type for an immutably borrowed value from a RefCell<T>
.
See the module-level documentation for more.
Implementations§
source§impl<'b, T: ?Sized> Ref<'b, T>
impl<'b, T: ?Sized> Ref<'b, T>
sourcepub fn clone(orig: &Ref<'b, T>) -> Ref<'b, T>
pub fn clone(orig: &Ref<'b, T>) -> Ref<'b, T>
Copies a Ref
.
The RefCell
is already immutably borrowed, so this cannot fail.
This is an associated function that needs to be used as
Ref::clone(...)
. A Clone
implementation or a method would interfere
with the widespread use of r.borrow().clone()
to clone the contents of
a RefCell
.
sourcepub fn map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, U>where
F: FnOnce(&T) -> &U,
pub fn map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, U>where
F: FnOnce(&T) -> &U,
Make a new Ref
for a component of the borrowed data.
The RefCell
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 RefCell
used through Deref
.
Examples
use std::cell::{RefCell, Ref};
let c = RefCell::new((5, 'b'));
let b1: Ref<(u32, char)> = c.borrow();
let b2: Ref<u32> = Ref::map(b1, |t| &t.0);
assert_eq!(*b2, 5)