Struct std::cell::RefCell

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

A mutable memory location with dynamically checked borrow rules

See the module-level documentation for more.

Methods

impl<T> RefCell<T>

const fn new(value: T) -> RefCell<T>

Creates a new RefCell containing value.

Examples

fn main() { use std::cell::RefCell; let c = RefCell::new(5); }

use std::cell::RefCell;

let c = RefCell::new(5);

fn into_inner(self) -> T

Consumes the RefCell, returning the wrapped value.

Examples

fn main() { use std::cell::RefCell; let c = RefCell::new(5); let five = c.into_inner(); }

use std::cell::RefCell;

let c = RefCell::new(5);

let five = c.into_inner();

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

fn borrow_state(&self) -> BorrowState

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.

fn borrow(&self) -> Ref<T>

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.

Examples

fn main() { use std::cell::RefCell; let c = RefCell::new(5); let borrowed_five = c.borrow(); let borrowed_five2 = c.borrow(); }

use std::cell::RefCell;

let c = RefCell::new(5);

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

An example of panic:

fn main() { 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()); }

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());

fn borrow_mut(&self) -> RefMut<T>

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.

Examples

fn main() { use std::cell::RefCell; let c = RefCell::new(5); *c.borrow_mut() = 7; assert_eq!(*c.borrow(), 7); }

use std::cell::RefCell;

let c = RefCell::new(5);

*c.borrow_mut() = 7;

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

An example of panic:

fn main() { 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()); }

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());

unsafe fn as_unsafe_cell(&self) -> &UnsafeCell<T>

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.

fn get_mut(&mut self) -> &mut T

Unstable (cell_get_mut #33444)

Returns a mutable reference to the underlying data.

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

Trait Implementations

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

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

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

fn clone(&self) -> RefCell<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T> Default for RefCell<T> where T: Default

fn default() -> RefCell<T>

Returns the "default value" for a type.

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

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

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

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

This method returns an Ordering between self and other.

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

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.