1.0.0[][src]Struct std::cell::RefCell

pub struct RefCell<T> where
    T: ?Sized
{ /* fields omitted */ }

A mutable memory location with dynamically checked borrow rules

See the module-level documentation for more.

Methods

impl<T> RefCell<T>[src]

pub const fn new(value: T) -> RefCell<T>[src]

Creates a new RefCell containing value.

Examples

use std::cell::RefCell;

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

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

Consumes the RefCell, returning the wrapped value.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

let five = c.into_inner();Run

pub fn replace(&self, t: T) -> T1.24.0[src]

Replaces the wrapped value with a new one, returning the old value, without deinitializing either one.

This function corresponds to std::mem::replace.

Panics

Panics if the value is currently borrowed.

Examples

use std::cell::RefCell;
let cell = RefCell::new(5);
let old_value = cell.replace(6);
assert_eq!(old_value, 5);
assert_eq!(cell, RefCell::new(6));Run

pub fn replace_with<F>(&self, f: F) -> T where
    F: FnOnce(&mut T) -> T, 
1.35.0[src]

Replaces the wrapped value with a new one computed from f, returning the old value, without deinitializing either one.

Panics

Panics if the value is currently borrowed.

Examples

use std::cell::RefCell;
let cell = RefCell::new(5);
let old_value = cell.replace_with(|&mut old| old + 1);
assert_eq!(old_value, 5);
assert_eq!(cell, RefCell::new(6));Run

pub fn swap(&self, other: &RefCell<T>)1.24.0[src]

Swaps the wrapped value of self with the wrapped value of other, without deinitializing either one.

This function corresponds to std::mem::swap.

Panics

Panics if the value in either RefCell is currently borrowed.

Examples

use std::cell::RefCell;
let c = RefCell::new(5);
let d = RefCell::new(6);
c.swap(&d);
assert_eq!(c, RefCell::new(6));
assert_eq!(d, RefCell::new(5));Run

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

pub fn borrow(&self) -> Ref<T>[src]

Immutably borrows the wrapped value.

The borrow lasts until the returned Ref exits scope. Multiple immutable borrows can be taken out at the same time.

Panics

Panics if the value is currently mutably borrowed. For a non-panicking variant, use try_borrow.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

let borrowed_five = c.borrow();
let borrowed_five2 = c.borrow();Run

An example of panic:

use std::cell::RefCell;
use std::thread;

let result = thread::spawn(move || {
   let c = RefCell::new(5);
   let m = c.borrow_mut();

   let b = c.borrow(); // this causes a panic
}).join();

assert!(result.is_err());Run

pub fn try_borrow(&self) -> Result<Ref<T>, BorrowError>1.13.0[src]

Immutably borrows the wrapped value, returning an error if the value is currently mutably borrowed.

The borrow lasts until the returned Ref exits scope. Multiple immutable borrows can be taken out at the same time.

This is the non-panicking variant of borrow.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

{
    let m = c.borrow_mut();
    assert!(c.try_borrow().is_err());
}

{
    let m = c.borrow();
    assert!(c.try_borrow().is_ok());
}Run

pub fn borrow_mut(&self) -> RefMut<T>[src]

Mutably borrows the wrapped value.

The borrow lasts until the returned RefMut or all RefMuts derived from it exit scope. The value cannot be borrowed while this borrow is active.

Panics

Panics if the value is currently borrowed. For a non-panicking variant, use try_borrow_mut.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

*c.borrow_mut() = 7;

assert_eq!(*c.borrow(), 7);Run

An example of panic:

use std::cell::RefCell;
use std::thread;

let result = thread::spawn(move || {
   let c = RefCell::new(5);
   let m = c.borrow();

   let b = c.borrow_mut(); // this causes a panic
}).join();

assert!(result.is_err());Run

pub fn try_borrow_mut(&self) -> Result<RefMut<T>, BorrowMutError>1.13.0[src]

Mutably borrows the wrapped value, returning an error if the value is currently borrowed.

The borrow lasts until the returned RefMut or all RefMuts derived from it exit scope. The value cannot be borrowed while this borrow is active.

This is the non-panicking variant of borrow_mut.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

{
    let m = c.borrow();
    assert!(c.try_borrow_mut().is_err());
}

assert!(c.try_borrow_mut().is_ok());Run

pub fn as_ptr(&self) -> *mut T1.12.0[src]

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

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

let ptr = c.as_ptr();Run

Important traits for &'_ mut F
pub fn get_mut(&mut self) -> &mut T1.11.0[src]

Returns a mutable reference to the underlying data.

This call borrows RefCell mutably (at compile-time) so there is no need for dynamic checks.

However be cautious: this method expects self to be mutable, which is generally not the case when using a RefCell. Take a look at the borrow_mut method instead if self isn't mutable.

Also, please be aware that this method is only for special circumstances and is usually not what you want. In case of doubt, use borrow_mut instead.

Examples

use std::cell::RefCell;

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

assert_eq!(c, RefCell::new(6));Run

pub unsafe fn try_borrow_unguarded(&self) -> Result<&T, BorrowError>1.37.0[src]

Immutably borrows the wrapped value, returning an error if the value is currently mutably borrowed.

Safety

Unlike RefCell::borrow, this method is unsafe because it does not return a Ref, thus leaving the borrow flag untouched. Mutably borrowing the RefCell while the reference returned by this method is alive is undefined behaviour.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

{
    let m = c.borrow_mut();
    assert!(unsafe { c.try_borrow_unguarded() }.is_err());
}

{
    let m = c.borrow();
    assert!(unsafe { c.try_borrow_unguarded() }.is_ok());
}Run

Trait Implementations

impl<T> Eq for RefCell<T> where
    T: Eq + ?Sized
1.2.0[src]

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

impl<T> Debug for RefCell<T> where
    T: Debug + ?Sized
[src]

impl<T> PartialEq<RefCell<T>> for RefCell<T> where
    T: PartialEq<T> + ?Sized
[src]

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

Panics

Panics if the value in either RefCell is currently borrowed.

impl<T> PartialOrd<RefCell<T>> for RefCell<T> where
    T: PartialOrd<T> + ?Sized
1.10.0[src]

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

Panics

Panics if the value in either RefCell is currently borrowed.

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

Panics

Panics if the value in either RefCell is currently borrowed.

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

Panics

Panics if the value in either RefCell is currently borrowed.

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

Panics

Panics if the value in either RefCell is currently borrowed.

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

Panics

Panics if the value in either RefCell is currently borrowed.

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

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

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

impl<T> Ord for RefCell<T> where
    T: Ord + ?Sized
1.10.0[src]

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

Panics

Panics if the value in either RefCell is currently borrowed.

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

fn clone(&self) -> RefCell<T>[src]

Panics

Panics if the value is currently mutably borrowed.

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

fn default() -> RefCell<T>[src]

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

Auto Trait Implementations

impl<T: ?Sized> UnwindSafe for RefCell<T> where
    T: UnwindSafe

impl<T> !RefUnwindSafe for RefCell<T>

impl<T: ?Sized> Unpin for RefCell<T> where
    T: Unpin

Blanket Implementations

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

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

type Error = Infallible

The type returned in the event of a conversion error.

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

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

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

The type returned in the event of a conversion error.

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

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

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

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

type Owned = T

The resulting type after obtaining ownership.