# Struct std::boxed::Box 1.0.0 [−] [src]

    pub struct Box<T> where T: ?Sized(_);

A pointer type for heap allocation.

See the module-level documentation for more.

## Methods

### `impl<T> Box<T>`

#### `fn new(x: T) -> Box<T>`

Allocates memory on the heap and then places `x` into it.

# Examples

fn main() { let five = Box::new(5); }

    let five = Box::new(5);

### `impl<T> Box<T> where T: ?Sized`

#### `unsafe fn from_raw(raw: *mut T) -> Box<T>`
1.4.0

Constructs a box from a raw pointer.

After calling this function, the raw pointer is owned by the resulting `Box`. Specifically, the `Box` destructor will call the destructor of `T` and free the allocated memory. Since the way `Box` allocates and releases memory is unspecified, the only valid pointer to pass to this function is the one taken from another `Box` via the `Box::into_raw` function.

This function is unsafe because improper use may lead to memory problems. For example, a double-free may occur if the function is called twice on the same raw pointer.

#### `fn into_raw(b: Box<T>) -> *mut T`
1.4.0

Consumes the `Box`, returning the wrapped raw pointer.

After calling this function, the caller is responsible for the memory previously managed by the `Box`. In particular, the caller should properly destroy `T` and release the memory. The proper way to do so is to convert the raw pointer back into a `Box` with the `Box::from_raw` function.

# Examples

fn main() { let seventeen = Box::new(17); let raw = Box::into_raw(seventeen); let boxed_again = unsafe { Box::from_raw(raw) }; }

    let seventeen = Box::new(17);
    let raw = Box::into_raw(seventeen);
    let boxed_again = unsafe { Box::from_raw(raw) };

### `impl Box<Any + 'static>`

#### `fn downcast<T>(self) -> Result<Box<T>, Box<Any + 'static>> where T: Any`

Attempt to downcast the box to a concrete type.

### `impl Box<Any + 'static + Send>`

#### `fn downcast<T>(self) -> Result<Box<T>, Box<Any + 'static + Send>> where T: Any`

Attempt to downcast the box to a concrete type.

## Trait Implementations

### `impl<T> Boxed for Box<T>`

#### `type Data = T`

Unstable (`placement_new_protocol` #27779)

#### `type Place = IntermediateBox<T>`

Unstable (`placement_new_protocol` #27779)

#### `unsafe fn finalize(b: IntermediateBox<T>) -> Box<T>`

Unstable (`placement_new_protocol` #27779)

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

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

### `impl<T> Default for Box<[T]>`

#### `fn default() -> Box<[T]>`

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

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

Returns a new box with a `clone()` of this box's contents.

# Examples

fn main() { let x = Box::new(5); let y = x.clone(); }

    let x = Box::new(5);
    let y = x.clone();

#### `fn clone_from(&mut self, source: &Box<T>)`

Copies `source`'s contents into `self` without creating a new allocation.

# Examples

fn main() { let x = Box::new(5); let mut y = Box::new(10); y.clone_from(&x); assert_eq!(*y, 5); }

    let x = Box::new(5);
    let mut y = Box::new(10);

    y.clone_from(&x);

    assert_eq!(*y, 5);

### `impl Clone for Box<str>`
1.3.0

#### `fn clone(&self) -> Box<str>`

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

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

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

#### `fn ne(&self, other: &Box<T>) -> bool`

### `impl<T> PartialOrd<Box<T>> for Box<T> where T: PartialOrd<T> + ?Sized`

#### `fn partial_cmp(&self, other: &Box<T>) -> Option<Ordering>`

#### `fn lt(&self, other: &Box<T>) -> bool`

#### `fn le(&self, other: &Box<T>) -> bool`

#### `fn ge(&self, other: &Box<T>) -> bool`

#### `fn gt(&self, other: &Box<T>) -> bool`

### `impl<T> Ord for Box<T> where T: Ord + ?Sized`

#### `fn cmp(&self, other: &Box<T>) -> Ordering`

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

### `impl<T> Hash for Box<T> where T: Hash + ?Sized`

#### `fn hash<H>(&self, state: &mut H) where H: Hasher`

#### `fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher`
1.3.0

### `impl<T> From<T> for Box<T>`
1.6.0

#### `fn from(t: T) -> Box<T>`

### `impl<T> Display for Box<T> where T: Display + ?Sized`

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

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

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

### `impl<T> Pointer for Box<T> where T: ?Sized`

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

### `impl<T> Deref for Box<T> where T: ?Sized`

#### `type Target = T`

#### `fn deref(&self) -> &T`

### `impl<T> DerefMut for Box<T> where T: ?Sized`

#### `fn deref_mut(&mut self) -> &mut T`

### `impl<I> Iterator for Box<I> where I: Iterator + ?Sized`

#### `type Item = I::Item`

#### `fn next(&mut self) -> Option<I::Item>`

#### `fn size_hint(&self) -> (usize, Option<usize>)`

#### `fn count(self) -> usize`

#### `fn last(self) -> Option<Self::Item>`

#### `fn nth(&mut self, n: usize) -> Option<Self::Item>`

#### `fn chain<U>(self, other: U) -> Chain<Self, U::IntoIter> where U: IntoIterator<Item=Self::Item>`

#### `fn zip<U>(self, other: U) -> Zip<Self, U::IntoIter> where U: IntoIterator`

#### `fn map<B, F>(self, f: F) -> Map<Self, F> where F: FnMut(Self::Item) -> B`

#### `fn filter<P>(self, predicate: P) -> Filter<Self, P> where P: FnMut(&Self::Item) -> bool`

#### `fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where F: FnMut(Self::Item) -> Option<B>`

#### `fn enumerate(self) -> Enumerate<Self>`

#### `fn peekable(self) -> Peekable<Self>`

#### `fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where P: FnMut(&Self::Item) -> bool`

#### `fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where P: FnMut(&Self::Item) -> bool`

#### `fn skip(self, n: usize) -> Skip<Self>`

#### `fn take(self, n: usize) -> Take<Self>`

#### `fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where F: FnMut(&mut St, Self::Item) -> Option<B>`

#### `fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where F: FnMut(Self::Item) -> U, U: IntoIterator`

#### `fn fuse(self) -> Fuse<Self>`

#### `fn inspect<F>(self, f: F) -> Inspect<Self, F> where F: FnMut(&Self::Item) -> ()`

#### `fn by_ref(&mut self) -> &mut Self`

#### `fn collect<B>(self) -> B where B: FromIterator<Self::Item>`

#### `fn partition<B, F>(self, f: F) -> (B, B) where B: Default + Extend<Self::Item>, F: FnMut(&Self::Item) -> bool`

#### `fn fold<B, F>(self, init: B, f: F) -> B where F: FnMut(B, Self::Item) -> B`

#### `fn all<F>(&mut self, f: F) -> bool where F: FnMut(Self::Item) -> bool`

#### `fn any<F>(&mut self, f: F) -> bool where F: FnMut(Self::Item) -> bool`

#### `fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where P: FnMut(&Self::Item) -> bool`

#### `fn position<P>(&mut self, predicate: P) -> Option<usize> where P: FnMut(Self::Item) -> bool`

#### `fn rposition<P>(&mut self, predicate: P) -> Option<usize> where P: FnMut(Self::Item) -> bool, Self: ExactSizeIterator + DoubleEndedIterator`

#### `fn max(self) -> Option<Self::Item> where Self::Item: Ord`

#### `fn min(self) -> Option<Self::Item> where Self::Item: Ord`

#### `fn max_by_key<B, F>(self, f: F) -> Option<Self::Item> where B: Ord, F: FnMut(&Self::Item) -> B`
1.6.0

#### `fn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where B: Ord, F: FnMut(&Self::Item) -> B`
1.6.0

#### `fn rev(self) -> Rev<Self> where Self: DoubleEndedIterator`

#### `fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where FromA: Default + Extend<A>, FromB: Default + Extend<B>, Self: Iterator<Item=(A, B)>`

#### `fn cloned<'a, T>(self) -> Cloned<Self> where Self: Iterator<Item=&'a T>, T: 'a + Clone`

#### `fn cycle(self) -> Cycle<Self> where Self: Clone`

#### `fn sum<S>(self) -> S where S: Add<Self::Item, Output=S> + Zero`

#### `fn product<P>(self) -> P where P: Mul<Self::Item, Output=P> + One`

#### `fn cmp<I>(self, other: I) -> Ordering where I: IntoIterator<Item=Self::Item>, Self::Item: Ord`
1.5.0

#### `fn partial_cmp<I>(self, other: I) -> Option<Ordering> where I: IntoIterator, Self::Item: PartialOrd<I::Item>`
1.5.0

#### `fn eq<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialEq<I::Item>`
1.5.0

#### `fn ne<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialEq<I::Item>`
1.5.0

#### `fn lt<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialOrd<I::Item>`
1.5.0

#### `fn le<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialOrd<I::Item>`
1.5.0

#### `fn gt<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialOrd<I::Item>`
1.5.0

#### `fn ge<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialOrd<I::Item>`
1.5.0

### `impl<I> DoubleEndedIterator for Box<I> where I: DoubleEndedIterator + ?Sized`

#### `fn next_back(&mut self) -> Option<I::Item>`

### `impl<I> ExactSizeIterator for Box<I> where I: ExactSizeIterator + ?Sized`

#### `fn len(&self) -> usize`

### `impl<'a, A, R> FnOnce<A> for Box<FnBox<A, Output=R> + 'a>`

#### `type Output = R`

Unstable (`fnbox` #28796)

: will be deprecated if and when Box becomes usable

#### `extern "rust-call" fn call_once(self, args: A) -> R`

Unstable (`fnbox` #28796)

: will be deprecated if and when Box becomes usable

### `impl<'a, A, R> FnOnce<A> for Box<FnBox<A, Output=R> + 'a + Send>`

#### `type Output = R`

Unstable (`fnbox` #28796)

: will be deprecated if and when Box becomes usable

#### `extern "rust-call" fn call_once(self, args: A) -> R`

Unstable (`fnbox` #28796)

: will be deprecated if and when Box becomes usable

### `impl<T, U> CoerceUnsized<Box<U>> for Box<T> where T: Unsize<U> + ?Sized, U: ?Sized`

### `impl<T> Clone for Box<[T]> where T: Clone`
1.3.0

#### `fn clone(&self) -> Box<[T]>`

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

### `impl<T> Borrow<T> for Box<T> where T: ?Sized`

#### `fn borrow(&self) -> &T`

### `impl<T> BorrowMut<T> for Box<T> where T: ?Sized`

#### `fn borrow_mut(&mut self) -> &mut T`

### `impl<T> AsRef<T> for Box<T> where T: ?Sized`
1.5.0

#### `fn as_ref(&self) -> &T`

### `impl<T> AsMut<T> for Box<T> where T: ?Sized`
1.5.0

#### `fn as_mut(&mut self) -> &mut T`

### `impl<'a, E: Error + 'a> From<E> for Box<Error + 'a>`
[src]

#### `fn from(err: E) -> Box<Error + 'a>`

### `impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<Error + Send + Sync + 'a>`
[src]

#### `fn from(err: E) -> Box<Error + Send + Sync + 'a>`

### `impl From<String> for Box<Error + Send + Sync>`
[src]

#### `fn from(err: String) -> Box<Error + Send + Sync>`

### `impl From<String> for Box<Error>`
1.7.0
[src]

#### `fn from(str_err: String) -> Box<Error>`

### `impl<'a, 'b> From<&'b str> for Box<Error + Send + Sync + 'a>`
[src]

#### `fn from(err: &'b str) -> Box<Error + Send + Sync + 'a>`

### `impl<'a> From<&'a str> for Box<Error>`
1.7.0
[src]

#### `fn from(err: &'a str) -> Box<Error>`

### `impl<T: Error> Error for Box<T>`
1.7.0
[src]

#### `fn description(&self) -> &str`

#### `fn cause(&self) -> Option<&Error>`

### `impl<R: Read + ?Sized> Read for Box<R>`
[src]

#### `fn read(&mut self, buf: &mut [u8]) -> Result<usize>`

#### `fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>`

#### `fn read_to_string(&mut self, buf: &mut String) -> Result<usize>`

#### `fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>`

#### `fn by_ref(&mut self) -> &mut Self where Self: Sized`

#### `fn bytes(self) -> Bytes<Self> where Self: Sized`

#### `fn chars(self) -> Chars<Self> where Self: Sized`

#### `fn chain<R: Read>(self, next: R) -> Chain<Self, R> where Self: Sized`

#### `fn take(self, limit: u64) -> Take<Self> where Self: Sized`

### `impl<W: Write + ?Sized> Write for Box<W>`
[src]

#### `fn write(&mut self, buf: &[u8]) -> Result<usize>`

#### `fn flush(&mut self) -> Result<()>`

#### `fn write_all(&mut self, buf: &[u8]) -> Result<()>`

#### `fn write_fmt(&mut self, fmt: Arguments) -> Result<()>`

#### `fn by_ref(&mut self) -> &mut Self where Self: Sized`

### `impl<S: Seek + ?Sized> Seek for Box<S>`
[src]

#### `fn seek(&mut self, pos: SeekFrom) -> Result<u64>`

### `impl<B: BufRead + ?Sized> BufRead for Box<B>`
[src]

#### `fn fill_buf(&mut self) -> Result<&[u8]>`

#### `fn consume(&mut self, amt: usize)`

#### `fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize>`

#### `fn read_line(&mut self, buf: &mut String) -> Result<usize>`

#### `fn split(self, byte: u8) -> Split<Self> where Self: Sized`

#### `fn lines(self) -> Lines<Self> where Self: Sized`

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