Struct std::cell::Ref

pub struct Ref<'b, T> where T: 'b + ?Sized {
    // some fields omitted
}

Wraps a borrowed reference to a value in a RefCell`RefCellbox. A wrapper type for an immutably borrowed value from aRefCell`.

See the module-level documentation for more.

Methods

impl<'b, T> Ref<'b, T> where T: ?Sized

fn clone(orig: &Ref<'b, T>) -> Ref<'b, T>

Unstable

: likely to be moved to a method, pending language changes

Copies a Ref`Ref`.

The RefCell`RefCell` is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::clone(...). A Clone`Cloneimplementation or a method would interfere with the widespread use ofr.borrow().clone()to clone the contents of aRefCell`.

fn map<U, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, U> where U: ?Sized, F: FnOnce(&T) -> &U

Unstable

: recently added

Make a new Ref`Ref` for a component of the borrowed data.

The RefCell`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`RefCellused throughDeref`.

Example

#![feature(cell_extras)] fn main() { 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) }

#![feature(cell_extras)]

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)

fn filter_map<U, F>(orig: Ref<'b, T>, f: F) -> Option<Ref<'b, U>> where F: FnOnce(&T) -> Option<&U>, U: ?Sized

Unstable

: recently added

Make a new Ref`Ref` for a optional component of the borrowed data, e.g. an enum variant.

The RefCell`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`RefCellused throughDeref`.

Example

#![feature(cell_extras)] fn main() { use std::cell::{RefCell, Ref}; let c = RefCell::new(Ok(5)); let b1: Ref<Result<u32, ()>> = c.borrow(); let b2: Ref<u32> = Ref::filter_map(b1, |o| o.as_ref().ok()).unwrap(); assert_eq!(*b2, 5) }

use std::cell::{RefCell, Ref};

let c = RefCell::new(Ok(5));
let b1: Ref<Result<u32, ()>> = c.borrow();
let b2: Ref<u32> = Ref::filter_map(b1, |o| o.as_ref().ok()).unwrap();
assert_eq!(*b2, 5)

Trait Implementations

impl<'b, T> Deref for Ref<'b, T> where T: ?Sized

type Target = T

fn deref(&'a self) -> &'a T

impl<'b, T> Debug for Ref<'b, T> where T: Debug + ?Sized

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>