Struct std::cell::RefCell1.0.0[][src]

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>
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Creates a new RefCell containing value.

Examples

use std::cell::RefCell;

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

Consumes the RefCell, returning the wrapped value.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

let five = c.into_inner();Run

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

🔬 This is a nightly-only experimental API. (refcell_replace_swap #43570)

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

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

Panics

Panics if the value is currently borrowed.

Examples

#![feature(refcell_replace_swap)]
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

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
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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

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

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

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

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 &'a mut I

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

Trait Implementations

impl<T> Clone for RefCell<T> where
    T: Clone
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Panics

Panics if the value is currently mutably borrowed.

Performs copy-assignment from source. Read more

impl<T> PartialOrd<RefCell<T>> for RefCell<T> where
    T: PartialOrd<T> + ?Sized
1.10.0
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Panics

Panics if the value in either RefCell is currently borrowed.

Panics

Panics if the value in either RefCell is currently borrowed.

Panics

Panics if the value in either RefCell is currently borrowed.

Panics

Panics if the value in either RefCell is currently borrowed.

Panics

Panics if the value in either RefCell is currently borrowed.

impl<T> Eq for RefCell<T> where
    T: Eq + ?Sized
1.2.0
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impl<T, U> CoerceUnsized<RefCell<U>> for RefCell<T> where
    T: CoerceUnsized<U>, 
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impl<T> Debug for RefCell<T> where
    T: Debug + ?Sized
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Formats the value using the given formatter. Read more

impl<T> From<T> for RefCell<T>
1.12.0
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Performs the conversion.

impl<T> Ord for RefCell<T> where
    T: Ord + ?Sized
1.10.0
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Panics

Panics if the value in either RefCell is currently borrowed.

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

impl<T> PartialEq<RefCell<T>> for RefCell<T> where
    T: PartialEq<T> + ?Sized
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Panics

Panics if the value in either RefCell is currently borrowed.

This method tests for !=.

impl<T> !Sync for RefCell<T> where
    T: ?Sized
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impl<T> Default for RefCell<T> where
    T: Default
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Creates a RefCell<T>, with the Default value for T.

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