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Struct std::cell::Cell

#[repr(transparent)]
pub struct Cell<T> where    T: ?Sized,  { /* fields omitted */ }

A mutable memory location.

Examples

Here you can see how using Cell<T> allows to use mutable field inside immutable struct (which is also called 'interior mutability').

use std::cell::Cell;

struct SomeStruct {
    regular_field: u8,
    special_field: Cell<u8>,
}

let my_struct = SomeStruct {
    regular_field: 0,
    special_field: Cell::new(1),
};

let new_value = 100;

// ERROR, because my_struct is immutable
// my_struct.regular_field = new_value;

// WORKS, although `my_struct` is immutable, field `special_field` is mutable because it is Cell
my_struct.special_field.set(new_value);
assert_eq!(my_struct.special_field.get(), new_value);

See the module-level documentation for more.

Methods

impl<T> Cell<T> where
    T: Copy
[src]

Returns a copy of the contained value.

Examples

use std::cell::Cell;

let c = Cell::new(5);

let five = c.get();

🔬 This is a nightly-only experimental API. (cell_update #50186)

Updates the contained value using a function and returns the new value.

Examples

#![feature(cell_update)]

use std::cell::Cell;

let c = Cell::new(5);
let new = c.update(|x| x + 1);

assert_eq!(new, 6);
assert_eq!(c.get(), 6);

impl<T> Cell<T> [src]

Creates a new Cell containing the given value.

Examples

use std::cell::Cell;

let c = Cell::new(5);

Sets the contained value.

Examples

use std::cell::Cell;

let c = Cell::new(5);

c.set(10);

Swaps the values of two Cells. Difference with std::mem::swap is that this function doesn't require &mut reference.

Examples

use std::cell::Cell;

let c1 = Cell::new(5i32);
let c2 = Cell::new(10i32);
c1.swap(&c2);
assert_eq!(10, c1.get());
assert_eq!(5, c2.get());

Replaces the contained value, and returns it.

Examples

use std::cell::Cell;

let cell = Cell::new(5);
assert_eq!(cell.get(), 5);
assert_eq!(cell.replace(10), 5);
assert_eq!(cell.get(), 10);

Unwraps the value.

Examples

use std::cell::Cell;

let c = Cell::new(5);
let five = c.into_inner();

assert_eq!(five, 5);

impl<T> Cell<T> where
    T: ?Sized
[src]

Returns a raw pointer to the underlying data in this cell.

Examples

use std::cell::Cell;

let c = Cell::new(5);

let ptr = c.as_ptr();

ⓘImportant traits for &'a mut I
impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'a, R: Read + ?Sized> Read for &'a mut R
impl<'a, W: Write + ?Sized> Write for &'a mut W

Returns a mutable reference to the underlying data.

This call borrows Cell mutably (at compile-time) which guarantees that we possess the only reference.

Examples

use std::cell::Cell;

let mut c = Cell::new(5);
*c.get_mut() += 1;

assert_eq!(c.get(), 6);

🔬 This is a nightly-only experimental API. (as_cell #43038)

Returns a &Cell<T> from a &mut T

Examples

#![feature(as_cell)]
use std::cell::Cell;

let slice: &mut [i32] = &mut [1, 2, 3];
let cell_slice: &Cell<[i32]> = Cell::from_mut(slice);
let slice_cell: &[Cell<i32>] = cell_slice.as_slice_of_cells();

assert_eq!(slice_cell.len(), 3);

impl<T> Cell<T> where
    T: Default
[src]

Takes the value of the cell, leaving Default::default() in its place.

Examples

use std::cell::Cell;

let c = Cell::new(5);
let five = c.take();

assert_eq!(five, 5);
assert_eq!(c.into_inner(), 0);

impl<T> Cell<[T]> [src]

ⓘImportant traits for &'a [u8]
impl<'a> Read for &'a [u8]
impl<'a> Write for &'a mut [u8]
🔬 This is a nightly-only experimental API. (as_cell #43038)

Returns a &[Cell<T>] from a &Cell<[T]>

Examples

#![feature(as_cell)]
use std::cell::Cell;

let slice: &mut [i32] = &mut [1, 2, 3];
let cell_slice: &Cell<[i32]> = Cell::from_mut(slice);
let slice_cell: &[Cell<i32>] = cell_slice.as_slice_of_cells();

assert_eq!(slice_cell.len(), 3);

Trait Implementations

impl<T> Clone for Cell<T> where
    T: Copy
[src]

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl<T> PartialOrd<Cell<T>> for Cell<T> where
    T: Copy + PartialOrd<T>, 
[src]
1.10.0

This method returns an ordering between self and other values if one exists. Read more

This method tests less than (for self and other) and is used by the < operator. Read more

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

This method tests greater than (for self and other) and is used by the > operator. Read more

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

impl<T> Ord for Cell<T> where
    T: Copy + Ord
[src]
1.10.0

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

impl<T> Debug for Cell<T> where
    T: Copy + Debug
[src]

Formats the value using the given formatter. Read more

impl<T> Eq for Cell<T> where
    T: Copy + Eq
[src]
1.2.0

impl<T, U> CoerceUnsized<Cell<U>> for Cell<T> where
    T: CoerceUnsized<U>, 
[src]

impl<T> PartialEq<Cell<T>> for Cell<T> where
    T: Copy + PartialEq<T>, 
[src]

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

impl<T> From<T> for Cell<T> [src]
1.12.0

Performs the conversion.

impl<T> !Sync for Cell<T> where
    T: ?Sized
[src]

impl<T> Default for Cell<T> where
    T: Default
[src]

Creates a Cell<T>, with the Default value for T.

impl<T> Send for Cell<T> where
    T: Send + ?Sized
[src]

Blanket Implementations

impl<T, U> TryFrom for T where
    T: From<U>, 
[src]

🔬 This is a nightly-only experimental API. (try_from #33417)

The type returned in the event of a conversion error.

🔬 This is a nightly-only experimental API. (try_from #33417)

Performs the conversion.

impl<T> From for T [src]

Performs the conversion.

impl<T, U> TryInto for T where
    U: TryFrom<T>, 
[src]

🔬 This is a nightly-only experimental API. (try_from #33417)

The type returned in the event of a conversion error.

🔬 This is a nightly-only experimental API. (try_from #33417)

Performs the conversion.

impl<T, U> Into for T where
    U: From<T>, 
[src]

Performs the conversion.

impl<T> Borrow for T where
    T: ?Sized
[src]

ⓘImportant traits for &'a mut I
impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'a, R: Read + ?Sized> Read for &'a mut R
impl<'a, W: Write + ?Sized> Write for &'a mut W

Immutably borrows from an owned value. Read more

impl<T> BorrowMut for T where
    T: ?Sized
[src]

ⓘImportant traits for &'a mut I
impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'a, R: Read + ?Sized> Read for &'a mut R
impl<'a, W: Write + ?Sized> Write for &'a mut W

Mutably borrows from an owned value. Read more

impl<T> Any for T where
    T: 'static + ?Sized
[src]

🔬 This is a nightly-only experimental API. (get_type_id #27745)this method will likely be replaced by an associated static

Gets the TypeId of self. Read more

impl<T> ToOwned for T where
    T: Clone
[src]

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into #41263)recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/cell/struct.Cell.html