# Struct std::cell::RefCell [−] [src]

    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); let borrowed_five = c.borrow_mut(); }

    use std::cell::RefCell;

    let c = RefCell::new(5);

    let borrowed_five = c.borrow_mut();

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.

## Trait Implementations

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

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

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

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

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

#### `fn default() -> RefCell<T>`

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

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

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

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

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

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

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