std::cell::Cell - Rust
Description: API documentation for the Rust `Cell` struct in crate `std`.
Keywords: rust, rustlang, rust-lang, Cell

# 1.0.0[−][src]Struct std::cell::Cell

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

A mutable memory location.

# Examples

In this example, you can see that `Cell<T>` enables mutation inside an immutable struct. In other words, it enables "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: `my_struct` is immutable
    // my_struct.regular_field = new_value;

    // WORKS: although `my_struct` is immutable, `special_field` is a `Cell`,
    // which can always be mutated
    my_struct.special_field.set(new_value);
    assert_eq!(my_struct.special_field.get(), new_value);Run

See the module-level documentation for more.

## Methods

### `impl<T> Cell<T> where
T: Copy,` [src]

#### `pub fn get(&self) -> T`[src]

Returns a copy of the contained value.

# Examples

    use std::cell::Cell;

    let c = Cell::new(5);

    let five = c.get();Run

#### `pub fn update<F>(&self, f: F) -> T where
F: FnOnce(T) -> T,` [src]

🔬 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);Run

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

#### `pub const fn new(value: T) -> Cell<T>`[src]

Creates a new `Cell` containing the given value.

# Examples

    use std::cell::Cell;

    let c = Cell::new(5);Run

#### `pub fn set(&self, val: T)`[src]

Sets the contained value.

# Examples

    use std::cell::Cell;

    let c = Cell::new(5);

    c.set(10);Run

#### `pub fn swap(&self, other: &Cell<T>)`
1.17.0
[src]

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());Run

#### `pub fn replace(&self, val: T) -> T`
1.17.0
[src]

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);Run

#### `pub fn into_inner(self) -> T`
1.17.0
[src]

Unwraps the value.

# Examples

    use std::cell::Cell;

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

    assert_eq!(five, 5);Run

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

#### `pub const fn as_ptr(&self) -> *mut T`
1.12.0
[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();Run

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`pub fn get_mut(&mut self) -> &mut T`
1.11.0
[src]

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);Run

#### `pub fn from_mut(t: &mut T) -> &Cell<T>`[src]

🔬 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);Run

### `impl<T> Cell<T> where
T: Default,` [src]

#### `pub fn take(&self) -> T`
1.17.0
[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);Run

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

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`
`pub fn as_slice_of_cells(&self) -> &[Cell<T>]`[src]

🔬 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);Run

## Trait Implementations

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

#### `fn default() -> Cell<T>`[src]

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

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

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

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

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`[src]

Formats the value using the given formatter. Read more

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

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

#### `fn clone(&self) -> Cell<T>`[src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)`[src]

Performs copy-assignment from `source`. Read more

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

#### `fn partial_cmp(&self, other: &Cell<T>) -> Option<Ordering>`[src]

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

#### `fn lt(&self, other: &Cell<T>) -> bool`[src]

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

#### `fn le(&self, other: &Cell<T>) -> bool`[src]

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

#### `fn gt(&self, other: &Cell<T>) -> bool`[src]

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

#### `fn ge(&self, other: &Cell<T>) -> bool`[src]

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,`
1.10.0
[src]

#### `fn cmp(&self, other: &Cell<T>) -> Ordering`[src]

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

#### `fn max(self, other: Self) -> Self`
1.21.0
[src]

Compares and returns the maximum of two values. Read more

#### `fn min(self, other: Self) -> Self`
1.21.0
[src]

Compares and returns the minimum of two values. Read more

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

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

#### `fn eq(&self, other: &Cell<T>) -> bool`[src]

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

#### `
#[must_use]
fn ne(&self, other: &Rhs) -> bool`[src]

This method tests for `!=`.

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

#### `fn from(t: T) -> Cell<T>`[src]

Performs the conversion.

## Blanket Implementations

### `impl<T> From for T`[src]

#### `fn from(t: T) -> T`[src]

Performs the conversion.

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

#### `type Error = !`

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

The type returned in the event of a conversion error.

#### `fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>`[src]

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

Performs the conversion.

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

#### `type Error = <U as TryFrom<T>>::Error`

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

The type returned in the event of a conversion error.

#### `fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>`[src]

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

Performs the conversion.

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

#### `fn into(self) -> U`[src]

Performs the conversion.

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

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

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

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`
`fn borrow_mut(&mut self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

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

#### `fn get_type_id(&self) -> TypeId`[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]

#### `type Owned = T`

#### `fn to_owned(&self) -> T`[src]

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

#### `fn clone_into(&self, target: &mut T)`[src]

🔬 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

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