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>
1.15.0 · 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
.
1.8.0 · sourcepub fn map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, U>
pub fn map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, U>
Makes 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)
Run1.63.0 · sourcepub fn filter_map<U: ?Sized, F>(
orig: Ref<'b, T>,
f: F
) -> Result<Ref<'b, U>, Self>
pub fn filter_map<U: ?Sized, F>( orig: Ref<'b, T>, f: F ) -> Result<Ref<'b, U>, Self>
Makes a new Ref
for an optional component of the borrowed data. The
original guard is returned as an Err(..)
if the closure returns
None
.
The RefCell
is already immutably borrowed, so this cannot fail.
This is an associated function that needs to be used as
Ref::filter_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(vec![1, 2, 3]);
let b1: Ref<'_, Vec<u32>> = c.borrow();
let b2: Result<Ref<'_, u32>, _> = Ref::filter_map(b1, |v| v.get(1));
assert_eq!(*b2.unwrap(), 2);
Run1.35.0 · sourcepub fn map_split<U: ?Sized, V: ?Sized, F>(
orig: Ref<'b, T>,
f: F
) -> (Ref<'b, U>, Ref<'b, V>)
pub fn map_split<U: ?Sized, V: ?Sized, F>( orig: Ref<'b, T>, f: F ) -> (Ref<'b, U>, Ref<'b, V>)
Splits a Ref
into multiple Ref
s for different components 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_split(...)
. A method would interfere with methods of the same
name on the contents of a RefCell
used through Deref
.
§Examples
use std::cell::{Ref, RefCell};
let cell = RefCell::new([1, 2, 3, 4]);
let borrow = cell.borrow();
let (begin, end) = Ref::map_split(borrow, |slice| slice.split_at(2));
assert_eq!(*begin, [1, 2]);
assert_eq!(*end, [3, 4]);
Runsourcepub fn leak(orig: Ref<'b, T>) -> &'b T
🔬This is a nightly-only experimental API. (cell_leak
#69099)
pub fn leak(orig: Ref<'b, T>) -> &'b T
cell_leak
#69099)Convert into a reference to the underlying data.
The underlying RefCell
can never be mutably borrowed from again and will always appear
already immutably borrowed. It is not a good idea to leak more than a constant number of
references. The RefCell
can be immutably borrowed again if only a smaller number of leaks
have occurred in total.
This is an associated function that needs to be used as
Ref::leak(...)
. A method would interfere with methods of the
same name on the contents of a RefCell
used through Deref
.
§Examples
#![feature(cell_leak)]
use std::cell::{RefCell, Ref};
let cell = RefCell::new(0);
let value = Ref::leak(cell.borrow());
assert_eq!(*value, 0);
assert!(cell.try_borrow().is_ok());
assert!(cell.try_borrow_mut().is_err());
Run