Struct std::cell::Ref

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

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.

Methods

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

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.

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

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

🔬 This is a nightly-only experimental API. (refcell_map_split #51476)

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

#![feature(refcell_map_split)]
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]);

Trait Implementations

impl<'_, T> Display for Ref<'_, T> where
    T: Display + ?Sized, 

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

Formats the value using the given formatter.

impl<'b, T, U> CoerceUnsized<Ref<'b, U>> for Ref<'b, T> where
    T: Unsize<U> + ?Sized,
    U: ?Sized, 

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

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

Formats the value using the given formatter.

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

type Target = T

The resulting type after dereferencing.

Important traits for &'_ mut I

impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

fn deref(&self) -> &T

Dereferences the value.