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

impl<T> RefCell<T> where T: ?Sized
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Unstable (borrow_state #27733)

Query the current state of this RefCell

The returned value can be dispatched on to determine if a call to borrow or borrow_mut would succeed.

Examples

#![feature(borrow_state)]

use std::cell::{BorrowState, RefCell};

let c = RefCell::new(5);

match c.borrow_state() {
    BorrowState::Writing => println!("Cannot be borrowed"),
    BorrowState::Reading => println!("Cannot be borrowed mutably"),
    BorrowState::Unused => println!("Can be borrowed (mutably as well)"),
}Run

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 exits 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 exits 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

Deprecated since 1.12.0

: renamed to as_ptr

Unstable (as_unsafe_cell #27708)

Returns a reference to the underlying UnsafeCell.

This can be used to circumvent RefCell's safety checks.

This function is unsafe because UnsafeCell's field is public.

Examples

#![feature(as_unsafe_cell)]

use std::cell::RefCell;

let c = RefCell::new(5);
let c = unsafe { c.as_unsafe_cell() };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

Returns a mutable reference to the underlying data.

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

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

impl<T> !Sync for RefCell<T> where T: ?Sized
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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.

impl<T> Ord for RefCell<T> where T: Ord + ?Sized
1.10.0
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This method returns an Ordering between self and other. Read more

impl<T> PartialOrd<RefCell<T>> for RefCell<T> where T: PartialOrd<T> + ?Sized
1.10.0
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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> PartialEq<RefCell<T>> for RefCell<T> where T: PartialEq<T> + ?Sized
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This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

impl<T> Send for RefCell<T> where T: Send + ?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> Clone for RefCell<T> where T: Clone
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Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

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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