Struct std::cell::Ref 1.0.0[−][src]
pub struct Ref<'b, T> where
T: 'b + ?Sized, { /* fields omitted */ }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
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.
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)pub fn filter_map<U, F>(
orig: Ref<'b, T>,
f: F
) -> Result<Ref<'b, U>, Ref<'b, T>> where
F: FnOnce(&T) -> Option<&U>,
U: ?Sized,
pub fn filter_map<U, F>(
orig: Ref<'b, T>,
f: F
) -> Result<Ref<'b, U>, Ref<'b, T>> where
F: FnOnce(&T) -> Option<&U>,
U: ?Sized,
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
#![feature(cell_filter_map)]
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);Splits a Ref into multiple Refs 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]);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());