pub struct Box<T: ?Sized, A: Allocator = Global>(/* private fields */);
Expand description
A pointer type that uniquely owns a heap allocation of type T
.
See the module-level documentation for more.
Implementations§
source§impl<T> Box<T>
impl<T> Box<T>
1.0.0 · sourcepub fn new(x: T) -> Self
pub fn new(x: T) -> Self
Allocates memory on the heap and then places x
into it.
This doesn’t actually allocate if T
is zero-sized.
§Examples
1.82.0 · sourcepub fn new_uninit() -> Box<MaybeUninit<T>>
pub fn new_uninit() -> Box<MaybeUninit<T>>
Constructs a new box with uninitialized contents.
§Examples
sourcepub fn new_zeroed() -> Box<MaybeUninit<T>>
🔬This is a nightly-only experimental API. (new_zeroed_alloc
#129396)
pub fn new_zeroed() -> Box<MaybeUninit<T>>
new_zeroed_alloc
#129396)Constructs a new Box
with uninitialized contents, with the memory
being filled with 0
bytes.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
§Examples
1.33.0 · sourcepub fn pin(x: T) -> Pin<Box<T>>
pub fn pin(x: T) -> Pin<Box<T>>
Constructs a new Pin<Box<T>>
. If T
does not implement Unpin
, then
x
will be pinned in memory and unable to be moved.
Constructing and pinning of the Box
can also be done in two steps: Box::pin(x)
does the same as Box::into_pin(Box::new(x))
. Consider using
into_pin
if you already have a Box<T>
, or if you want to
construct a (pinned) Box
in a different way than with Box::new
.
sourcepub fn try_new(x: T) -> Result<Self, AllocError>
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn try_new(x: T) -> Result<Self, AllocError>
allocator_api
#32838)Allocates memory on the heap then places x
into it,
returning an error if the allocation fails
This doesn’t actually allocate if T
is zero-sized.
§Examples
sourcepub fn try_new_uninit() -> Result<Box<MaybeUninit<T>>, AllocError>
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn try_new_uninit() -> Result<Box<MaybeUninit<T>>, AllocError>
allocator_api
#32838)Constructs a new box with uninitialized contents on the heap, returning an error if the allocation fails
§Examples
sourcepub fn try_new_zeroed() -> Result<Box<MaybeUninit<T>>, AllocError>
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn try_new_zeroed() -> Result<Box<MaybeUninit<T>>, AllocError>
allocator_api
#32838)Constructs a new Box
with uninitialized contents, with the memory
being filled with 0
bytes on the heap
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
§Examples
source§impl<T, A: Allocator> Box<T, A>
impl<T, A: Allocator> Box<T, A>
sourcepub fn new_in(x: T, alloc: A) -> Selfwhere
A: Allocator,
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn new_in(x: T, alloc: A) -> Selfwhere
A: Allocator,
allocator_api
#32838)Allocates memory in the given allocator then places x
into it.
This doesn’t actually allocate if T
is zero-sized.
§Examples
sourcepub fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError>where
A: Allocator,
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError>where
A: Allocator,
allocator_api
#32838)Allocates memory in the given allocator then places x
into it,
returning an error if the allocation fails
This doesn’t actually allocate if T
is zero-sized.
§Examples
sourcepub fn new_uninit_in(alloc: A) -> Box<MaybeUninit<T>, A>where
A: Allocator,
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn new_uninit_in(alloc: A) -> Box<MaybeUninit<T>, A>where
A: Allocator,
allocator_api
#32838)Constructs a new box with uninitialized contents in the provided allocator.
§Examples
sourcepub fn try_new_uninit_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError>where
A: Allocator,
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn try_new_uninit_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError>where
A: Allocator,
allocator_api
#32838)Constructs a new box with uninitialized contents in the provided allocator, returning an error if the allocation fails
§Examples
sourcepub fn new_zeroed_in(alloc: A) -> Box<MaybeUninit<T>, A>where
A: Allocator,
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn new_zeroed_in(alloc: A) -> Box<MaybeUninit<T>, A>where
A: Allocator,
allocator_api
#32838)Constructs a new Box
with uninitialized contents, with the memory
being filled with 0
bytes in the provided allocator.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
§Examples
sourcepub fn try_new_zeroed_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError>where
A: Allocator,
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn try_new_zeroed_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError>where
A: Allocator,
allocator_api
#32838)Constructs a new Box
with uninitialized contents, with the memory
being filled with 0
bytes in the provided allocator,
returning an error if the allocation fails,
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
§Examples
sourcepub fn pin_in(x: T, alloc: A) -> Pin<Self>where
A: 'static + Allocator,
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn pin_in(x: T, alloc: A) -> Pin<Self>where
A: 'static + Allocator,
allocator_api
#32838)Constructs a new Pin<Box<T, A>>
. If T
does not implement Unpin
, then
x
will be pinned in memory and unable to be moved.
Constructing and pinning of the Box
can also be done in two steps: Box::pin_in(x, alloc)
does the same as Box::into_pin(Box::new_in(x, alloc))
. Consider using
into_pin
if you already have a Box<T, A>
, or if you want to
construct a (pinned) Box
in a different way than with Box::new_in
.
sourcepub fn into_boxed_slice(boxed: Self) -> Box<[T], A>
🔬This is a nightly-only experimental API. (box_into_boxed_slice
#71582)
pub fn into_boxed_slice(boxed: Self) -> Box<[T], A>
box_into_boxed_slice
#71582)Converts a Box<T>
into a Box<[T]>
This conversion does not allocate on the heap and happens in place.
sourcepub fn into_inner(boxed: Self) -> T
🔬This is a nightly-only experimental API. (box_into_inner
#80437)
pub fn into_inner(boxed: Self) -> T
box_into_inner
#80437)Consumes the Box
, returning the wrapped value.
§Examples
source§impl<T> Box<[T]>
impl<T> Box<[T]>
1.82.0 · sourcepub fn new_uninit_slice(len: usize) -> Box<[MaybeUninit<T>]>
pub fn new_uninit_slice(len: usize) -> Box<[MaybeUninit<T>]>
Constructs a new boxed slice with uninitialized contents.
§Examples
sourcepub fn new_zeroed_slice(len: usize) -> Box<[MaybeUninit<T>]>
🔬This is a nightly-only experimental API. (new_zeroed_alloc
#129396)
pub fn new_zeroed_slice(len: usize) -> Box<[MaybeUninit<T>]>
new_zeroed_alloc
#129396)Constructs a new boxed slice with uninitialized contents, with the memory
being filled with 0
bytes.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
§Examples
sourcepub fn try_new_uninit_slice(
len: usize,
) -> Result<Box<[MaybeUninit<T>]>, AllocError>
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn try_new_uninit_slice( len: usize, ) -> Result<Box<[MaybeUninit<T>]>, AllocError>
allocator_api
#32838)Constructs a new boxed slice with uninitialized contents. Returns an error if the allocation fails.
§Examples
sourcepub fn try_new_zeroed_slice(
len: usize,
) -> Result<Box<[MaybeUninit<T>]>, AllocError>
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn try_new_zeroed_slice( len: usize, ) -> Result<Box<[MaybeUninit<T>]>, AllocError>
allocator_api
#32838)Constructs a new boxed slice with uninitialized contents, with the memory
being filled with 0
bytes. Returns an error if the allocation fails.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
§Examples
source§impl<T, A: Allocator> Box<[T], A>
impl<T, A: Allocator> Box<[T], A>
sourcepub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>
allocator_api
#32838)Constructs a new boxed slice with uninitialized contents in the provided allocator.
§Examples
#![feature(allocator_api)]
use std::alloc::System;
let mut values = Box::<[u32], _>::new_uninit_slice_in(3, System);
let values = unsafe {
// Deferred initialization:
values[0].as_mut_ptr().write(1);
values[1].as_mut_ptr().write(2);
values[2].as_mut_ptr().write(3);
values.assume_init()
};
assert_eq!(*values, [1, 2, 3])
sourcepub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>
allocator_api
#32838)Constructs a new boxed slice with uninitialized contents in the provided allocator,
with the memory being filled with 0
bytes.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
§Examples
sourcepub fn try_new_uninit_slice_in(
len: usize,
alloc: A,
) -> Result<Box<[MaybeUninit<T>], A>, AllocError>
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn try_new_uninit_slice_in( len: usize, alloc: A, ) -> Result<Box<[MaybeUninit<T>], A>, AllocError>
allocator_api
#32838)Constructs a new boxed slice with uninitialized contents in the provided allocator. Returns an error if the allocation fails.
§Examples
#![feature(allocator_api)]
use std::alloc::System;
let mut values = Box::<[u32], _>::try_new_uninit_slice_in(3, System)?;
let values = unsafe {
// Deferred initialization:
values[0].as_mut_ptr().write(1);
values[1].as_mut_ptr().write(2);
values[2].as_mut_ptr().write(3);
values.assume_init()
};
assert_eq!(*values, [1, 2, 3]);
sourcepub fn try_new_zeroed_slice_in(
len: usize,
alloc: A,
) -> Result<Box<[MaybeUninit<T>], A>, AllocError>
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn try_new_zeroed_slice_in( len: usize, alloc: A, ) -> Result<Box<[MaybeUninit<T>], A>, AllocError>
allocator_api
#32838)Constructs a new boxed slice with uninitialized contents in the provided allocator, with the memory
being filled with 0
bytes. Returns an error if the allocation fails.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
§Examples
source§impl<T, A: Allocator> Box<MaybeUninit<T>, A>
impl<T, A: Allocator> Box<MaybeUninit<T>, A>
1.82.0 · sourcepub unsafe fn assume_init(self) -> Box<T, A>
pub unsafe fn assume_init(self) -> Box<T, A>
Converts to Box<T, A>
.
§Safety
As with MaybeUninit::assume_init
,
it is up to the caller to guarantee that the value
really is in an initialized state.
Calling this when the content is not yet fully initialized
causes immediate undefined behavior.
§Examples
sourcepub fn write(boxed: Self, value: T) -> Box<T, A>
🔬This is a nightly-only experimental API. (box_uninit_write
#129397)
pub fn write(boxed: Self, value: T) -> Box<T, A>
box_uninit_write
#129397)Writes the value and converts to Box<T, A>
.
This method converts the box similarly to Box::assume_init
but
writes value
into it before conversion thus guaranteeing safety.
In some scenarios use of this method may improve performance because
the compiler may be able to optimize copying from stack.
§Examples
#![feature(box_uninit_write)]
let big_box = Box::<[usize; 1024]>::new_uninit();
let mut array = [0; 1024];
for (i, place) in array.iter_mut().enumerate() {
*place = i;
}
// The optimizer may be able to elide this copy, so previous code writes
// to heap directly.
let big_box = Box::write(big_box, array);
for (i, x) in big_box.iter().enumerate() {
assert_eq!(*x, i);
}
source§impl<T, A: Allocator> Box<[MaybeUninit<T>], A>
impl<T, A: Allocator> Box<[MaybeUninit<T>], A>
1.82.0 · sourcepub unsafe fn assume_init(self) -> Box<[T], A>
pub unsafe fn assume_init(self) -> Box<[T], A>
Converts to Box<[T], A>
.
§Safety
As with MaybeUninit::assume_init
,
it is up to the caller to guarantee that the values
really are in an initialized state.
Calling this when the content is not yet fully initialized
causes immediate undefined behavior.
§Examples
source§impl<T: ?Sized> Box<T>
impl<T: ?Sized> Box<T>
1.4.0 · sourcepub unsafe fn from_raw(raw: *mut T) -> Self
pub unsafe fn from_raw(raw: *mut T) -> Self
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. For this
to be safe, the memory must have been allocated in accordance
with the memory layout used by Box
.
§Safety
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.
The safety conditions are described in the memory layout section.
§Examples
Recreate a Box
which was previously converted to a raw pointer
using Box::into_raw
:
Manually create a Box
from scratch by using the global allocator:
use std::alloc::{alloc, Layout};
unsafe {
let ptr = alloc(Layout::new::<i32>()) as *mut i32;
// In general .write is required to avoid attempting to destruct
// the (uninitialized) previous contents of `ptr`, though for this
// simple example `*ptr = 5` would have worked as well.
ptr.write(5);
let x = Box::from_raw(ptr);
}
source§impl<T: ?Sized, A: Allocator> Box<T, A>
impl<T: ?Sized, A: Allocator> Box<T, A>
sourcepub const unsafe fn from_raw_in(raw: *mut T, alloc: A) -> Self
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub const unsafe fn from_raw_in(raw: *mut T, alloc: A) -> Self
allocator_api
#32838)Constructs a box from a raw pointer in the given allocator.
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. For this
to be safe, the memory must have been allocated in accordance
with the memory layout used by Box
.
§Safety
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.
§Examples
Recreate a Box
which was previously converted to a raw pointer
using Box::into_raw_with_allocator
:
#![feature(allocator_api)]
use std::alloc::System;
let x = Box::new_in(5, System);
let (ptr, alloc) = Box::into_raw_with_allocator(x);
let x = unsafe { Box::from_raw_in(ptr, alloc) };
Manually create a Box
from scratch by using the system allocator:
#![feature(allocator_api, slice_ptr_get)]
use std::alloc::{Allocator, Layout, System};
unsafe {
let ptr = System.allocate(Layout::new::<i32>())?.as_mut_ptr() as *mut i32;
// In general .write is required to avoid attempting to destruct
// the (uninitialized) previous contents of `ptr`, though for this
// simple example `*ptr = 5` would have worked as well.
ptr.write(5);
let x = Box::from_raw_in(ptr, System);
}
1.4.0 · sourcepub fn into_raw(b: Self) -> *mut T
pub fn into_raw(b: Self) -> *mut T
Consumes the Box
, returning a wrapped raw pointer.
The pointer will be properly aligned and non-null.
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, taking
into account the memory layout used by Box
. The easiest way to
do this is to convert the raw pointer back into a Box
with the
Box::from_raw
function, allowing the Box
destructor to perform
the cleanup.
Note: this is an associated function, which means that you have
to call it as Box::into_raw(b)
instead of b.into_raw()
. This
is so that there is no conflict with a method on the inner type.
§Examples
Converting the raw pointer back into a Box
with Box::from_raw
for automatic cleanup:
let x = Box::new(String::from("Hello"));
let ptr = Box::into_raw(x);
let x = unsafe { Box::from_raw(ptr) };
Manual cleanup by explicitly running the destructor and deallocating the memory:
use std::alloc::{dealloc, Layout};
use std::ptr;
let x = Box::new(String::from("Hello"));
let ptr = Box::into_raw(x);
unsafe {
ptr::drop_in_place(ptr);
dealloc(ptr as *mut u8, Layout::new::<String>());
}
Note: This is equivalent to the following:
sourcepub fn into_raw_with_allocator(b: Self) -> (*mut T, A)
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub fn into_raw_with_allocator(b: Self) -> (*mut T, A)
allocator_api
#32838)Consumes the Box
, returning a wrapped raw pointer and the allocator.
The pointer will be properly aligned and non-null.
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, taking
into account the memory layout used by Box
. The easiest way to
do this is to convert the raw pointer back into a Box
with the
Box::from_raw_in
function, allowing the Box
destructor to perform
the cleanup.
Note: this is an associated function, which means that you have
to call it as Box::into_raw_with_allocator(b)
instead of b.into_raw_with_allocator()
. This
is so that there is no conflict with a method on the inner type.
§Examples
Converting the raw pointer back into a Box
with Box::from_raw_in
for automatic cleanup:
#![feature(allocator_api)]
use std::alloc::System;
let x = Box::new_in(String::from("Hello"), System);
let (ptr, alloc) = Box::into_raw_with_allocator(x);
let x = unsafe { Box::from_raw_in(ptr, alloc) };
Manual cleanup by explicitly running the destructor and deallocating the memory:
#![feature(allocator_api)]
use std::alloc::{Allocator, Layout, System};
use std::ptr::{self, NonNull};
let x = Box::new_in(String::from("Hello"), System);
let (ptr, alloc) = Box::into_raw_with_allocator(x);
unsafe {
ptr::drop_in_place(ptr);
let non_null = NonNull::new_unchecked(ptr);
alloc.deallocate(non_null.cast(), Layout::new::<String>());
}
sourcepub fn as_mut_ptr(b: &mut Self) -> *mut T
🔬This is a nightly-only experimental API. (box_as_ptr
#129090)
pub fn as_mut_ptr(b: &mut Self) -> *mut T
box_as_ptr
#129090)Returns a raw mutable pointer to the Box
’s contents.
The caller must ensure that the Box
outlives the pointer this
function returns, or else it will end up dangling.
This method guarantees that for the purpose of the aliasing model, this method
does not materialize a reference to the underlying memory, and thus the returned pointer
will remain valid when mixed with other calls to as_ptr
and as_mut_ptr
.
Note that calling other methods that materialize references to the memory
may still invalidate this pointer.
See the example below for how this guarantee can be used.
§Examples
Due to the aliasing guarantee, the following code is legal:
sourcepub fn as_ptr(b: &Self) -> *const T
🔬This is a nightly-only experimental API. (box_as_ptr
#129090)
pub fn as_ptr(b: &Self) -> *const T
box_as_ptr
#129090)Returns a raw pointer to the Box
’s contents.
The caller must ensure that the Box
outlives the pointer this
function returns, or else it will end up dangling.
The caller must also ensure that the memory the pointer (non-transitively) points to
is never written to (except inside an UnsafeCell
) using this pointer or any pointer
derived from it. If you need to mutate the contents of the Box
, use as_mut_ptr
.
This method guarantees that for the purpose of the aliasing model, this method
does not materialize a reference to the underlying memory, and thus the returned pointer
will remain valid when mixed with other calls to as_ptr
and as_mut_ptr
.
Note that calling other methods that materialize mutable references to the memory,
as well as writing to this memory, may still invalidate this pointer.
See the example below for how this guarantee can be used.
§Examples
Due to the aliasing guarantee, the following code is legal:
#![feature(box_as_ptr)]
unsafe {
let mut v = Box::new(0);
let ptr1 = Box::as_ptr(&v);
let ptr2 = Box::as_mut_ptr(&mut v);
let _val = ptr2.read();
// No write to this memory has happened yet, so `ptr1` is still valid.
let _val = ptr1.read();
// However, once we do a write...
ptr2.write(1);
// ... `ptr1` is no longer valid.
// This would be UB: let _val = ptr1.read();
}
sourcepub const fn allocator(b: &Self) -> &A
🔬This is a nightly-only experimental API. (allocator_api
#32838)
pub const fn allocator(b: &Self) -> &A
allocator_api
#32838)Returns a reference to the underlying allocator.
Note: this is an associated function, which means that you have
to call it as Box::allocator(&b)
instead of b.allocator()
. This
is so that there is no conflict with a method on the inner type.
1.26.0 · sourcepub fn leak<'a>(b: Self) -> &'a mut Twhere
A: 'a,
pub fn leak<'a>(b: Self) -> &'a mut Twhere
A: 'a,
Consumes and leaks the Box
, returning a mutable reference,
&'a mut T
.
Note that the type T
must outlive the chosen lifetime 'a
. If the type
has only static references, or none at all, then this may be chosen to be
'static
.
This function is mainly useful for data that lives for the remainder of
the program’s life. Dropping the returned reference will cause a memory
leak. If this is not acceptable, the reference should first be wrapped
with the Box::from_raw
function producing a Box
. This Box
can
then be dropped which will properly destroy T
and release the
allocated memory.
Note: this is an associated function, which means that you have
to call it as Box::leak(b)
instead of b.leak()
. This
is so that there is no conflict with a method on the inner type.
§Examples
Simple usage:
let x = Box::new(41);
let static_ref: &'static mut usize = Box::leak(x);
*static_ref += 1;
assert_eq!(*static_ref, 42);
Unsized data:
1.63.0 (const: unstable) · sourcepub fn into_pin(boxed: Self) -> Pin<Self>where
A: 'static,
pub fn into_pin(boxed: Self) -> Pin<Self>where
A: 'static,
Converts a Box<T>
into a Pin<Box<T>>
. If T
does not implement Unpin
, then
*boxed
will be pinned in memory and unable to be moved.
This conversion does not allocate on the heap and happens in place.
This is also available via From
.
Constructing and pinning a Box
with Box::into_pin(Box::new(x))
can also be written more concisely using Box::pin(x)
.
This into_pin
method is useful if you already have a Box<T>
, or you are
constructing a (pinned) Box
in a different way than with Box::new
.
§Notes
It’s not recommended that crates add an impl like From<Box<T>> for Pin<T>
,
as it’ll introduce an ambiguity when calling Pin::from
.
A demonstration of such a poor impl is shown below.
struct Foo; // A type defined in this crate.
impl From<Box<()>> for Pin<Foo> {
fn from(_: Box<()>) -> Pin<Foo> {
Pin::new(Foo)
}
}
let foo = Box::new(());
let bar = Pin::from(foo);
source§impl<A: Allocator> Box<dyn Any, A>
impl<A: Allocator> Box<dyn Any, A>
1.0.0 · sourcepub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
Attempts to downcast the box to a concrete type.
§Examples
sourcepub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>
🔬This is a nightly-only experimental API. (downcast_unchecked
#90850)
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>
downcast_unchecked
#90850)Downcasts the box to a concrete type.
For a safe alternative see downcast
.
§Examples
#![feature(downcast_unchecked)]
use std::any::Any;
let x: Box<dyn Any> = Box::new(1_usize);
unsafe {
assert_eq!(*x.downcast_unchecked::<usize>(), 1);
}
§Safety
The contained value must be of type T
. Calling this method
with the incorrect type is undefined behavior.
source§impl<A: Allocator> Box<dyn Any + Send, A>
impl<A: Allocator> Box<dyn Any + Send, A>
1.0.0 · sourcepub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
Attempts to downcast the box to a concrete type.
§Examples
sourcepub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>
🔬This is a nightly-only experimental API. (downcast_unchecked
#90850)
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>
downcast_unchecked
#90850)Downcasts the box to a concrete type.
For a safe alternative see downcast
.
§Examples
#![feature(downcast_unchecked)]
use std::any::Any;
let x: Box<dyn Any + Send> = Box::new(1_usize);
unsafe {
assert_eq!(*x.downcast_unchecked::<usize>(), 1);
}
§Safety
The contained value must be of type T
. Calling this method
with the incorrect type is undefined behavior.
source§impl<A: Allocator> Box<dyn Any + Send + Sync, A>
impl<A: Allocator> Box<dyn Any + Send + Sync, A>
1.51.0 · sourcepub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
Attempts to downcast the box to a concrete type.
§Examples
sourcepub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>
🔬This is a nightly-only experimental API. (downcast_unchecked
#90850)
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>
downcast_unchecked
#90850)Downcasts the box to a concrete type.
For a safe alternative see downcast
.
§Examples
#![feature(downcast_unchecked)]
use std::any::Any;
let x: Box<dyn Any + Send + Sync> = Box::new(1_usize);
unsafe {
assert_eq!(*x.downcast_unchecked::<usize>(), 1);
}
§Safety
The contained value must be of type T
. Calling this method
with the incorrect type is undefined behavior.
Trait Implementations§
source§impl<Args: Tuple, F: AsyncFn<Args> + ?Sized, A: Allocator> AsyncFn<Args> for Box<F, A>
impl<Args: Tuple, F: AsyncFn<Args> + ?Sized, A: Allocator> AsyncFn<Args> for Box<F, A>
source§extern "rust-call" fn async_call(
&self,
args: Args,
) -> Self::CallRefFuture<'_>
extern "rust-call" fn async_call( &self, args: Args, ) -> Self::CallRefFuture<'_>
async_fn_traits
)AsyncFn
, returning a future which may borrow from the called closure.source§impl<Args: Tuple, F: AsyncFnMut<Args> + ?Sized, A: Allocator> AsyncFnMut<Args> for Box<F, A>
impl<Args: Tuple, F: AsyncFnMut<Args> + ?Sized, A: Allocator> AsyncFnMut<Args> for Box<F, A>
source§type CallRefFuture<'a> = <F as AsyncFnMut<Args>>::CallRefFuture<'a>
where
Self: 'a
type CallRefFuture<'a> = <F as AsyncFnMut<Args>>::CallRefFuture<'a> where Self: 'a
async_fn_traits
)AsyncFnMut::async_call_mut
and AsyncFn::async_call
.source§extern "rust-call" fn async_call_mut(
&mut self,
args: Args,
) -> Self::CallRefFuture<'_>
extern "rust-call" fn async_call_mut( &mut self, args: Args, ) -> Self::CallRefFuture<'_>
async_fn_traits
)AsyncFnMut
, returning a future which may borrow from the called closure.source§impl<Args: Tuple, F: AsyncFnOnce<Args> + ?Sized, A: Allocator> AsyncFnOnce<Args> for Box<F, A>
impl<Args: Tuple, F: AsyncFnOnce<Args> + ?Sized, A: Allocator> AsyncFnOnce<Args> for Box<F, A>
source§type Output = <F as AsyncFnOnce<Args>>::Output
type Output = <F as AsyncFnOnce<Args>>::Output
async_fn_traits
)source§type CallOnceFuture = <F as AsyncFnOnce<Args>>::CallOnceFuture
type CallOnceFuture = <F as AsyncFnOnce<Args>>::CallOnceFuture
async_fn_traits
)AsyncFnOnce::async_call_once
.source§extern "rust-call" fn async_call_once(
self,
args: Args,
) -> Self::CallOnceFuture
extern "rust-call" fn async_call_once( self, args: Args, ) -> Self::CallOnceFuture
async_fn_traits
)AsyncFnOnce
, returning a future which may move out of the called closure.source§impl<S: ?Sized + AsyncIterator + Unpin> AsyncIterator for Box<S>
impl<S: ?Sized + AsyncIterator + Unpin> AsyncIterator for Box<S>
source§type Item = <S as AsyncIterator>::Item
type Item = <S as AsyncIterator>::Item
async_iterator
#79024)source§fn poll_next(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<Self::Item>>
fn poll_next( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Option<Self::Item>>
async_iterator
#79024)None
if the async iterator is exhausted. Read more1.1.0 · source§impl<T: ?Sized, A: Allocator> BorrowMut<T> for Box<T, A>
impl<T: ?Sized, A: Allocator> BorrowMut<T> for Box<T, A>
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
1.3.0 · source§impl<T: Clone, A: Allocator + Clone> Clone for Box<[T], A>
impl<T: Clone, A: Allocator + Clone> Clone for Box<[T], A>
source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
Copies source
’s contents into self
without creating a new allocation,
so long as the two are of the same length.
§Examples
1.0.0 · source§impl<T: Clone, A: Allocator + Clone> Clone for Box<T, A>
impl<T: Clone, A: Allocator + Clone> Clone for Box<T, A>
source§impl<G: ?Sized + Coroutine<R> + Unpin, R, A: Allocator> Coroutine<R> for Box<G, A>
impl<G: ?Sized + Coroutine<R> + Unpin, R, A: Allocator> Coroutine<R> for Box<G, A>
source§type Yield = <G as Coroutine<R>>::Yield
type Yield = <G as Coroutine<R>>::Yield
coroutine_trait
#43122)source§impl<G: ?Sized + Coroutine<R>, R, A> Coroutine<R> for Pin<Box<G, A>>where
A: 'static + Allocator,
impl<G: ?Sized + Coroutine<R>, R, A> Coroutine<R> for Pin<Box<G, A>>where
A: 'static + Allocator,
source§type Yield = <G as Coroutine<R>>::Yield
type Yield = <G as Coroutine<R>>::Yield
coroutine_trait
#43122)1.0.0 · source§impl<I: DoubleEndedIterator + ?Sized, A: Allocator> DoubleEndedIterator for Box<I, A>
impl<I: DoubleEndedIterator + ?Sized, A: Allocator> DoubleEndedIterator for Box<I, A>
source§fn next_back(&mut self) -> Option<I::Item>
fn next_back(&mut self) -> Option<I::Item>
source§fn nth_back(&mut self, n: usize) -> Option<I::Item>
fn nth_back(&mut self, n: usize) -> Option<I::Item>
n
th element from the end of the iterator. Read moresource§fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>>
fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>>
iter_advance_by
#77404)n
elements. Read more1.27.0 · source§fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R
fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R
Iterator::try_fold()
: it takes
elements starting from the back of the iterator. Read more1.8.0 · source§impl<T: Error> Error for Box<T>
impl<T: Error> Error for Box<T>
source§fn description(&self) -> &str
fn description(&self) -> &str
source§fn cause(&self) -> Option<&dyn Error>
fn cause(&self) -> Option<&dyn Error>
1.0.0 · source§impl<I: ExactSizeIterator + ?Sized, A: Allocator> ExactSizeIterator for Box<I, A>
impl<I: ExactSizeIterator + ?Sized, A: Allocator> ExactSizeIterator for Box<I, A>
1.45.0 · source§impl<A: Allocator> Extend<Box<str, A>> for String
impl<A: Allocator> Extend<Box<str, A>> for String
1.35.0 · source§impl<Args: Tuple, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A>
impl<Args: Tuple, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A>
1.17.0 · source§impl<T: Clone> From<&[T]> for Box<[T]>
impl<T: Clone> From<&[T]> for Box<[T]>
1.6.0 · source§impl<'a> From<&str> for Box<dyn Error + 'a>
impl<'a> From<&str> for Box<dyn Error + 'a>
1.0.0 · source§impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a>
impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a>
1.33.0 · source§impl<T: ?Sized, A> From<Box<T, A>> for Pin<Box<T, A>>where
A: 'static + Allocator,
impl<T: ?Sized, A> From<Box<T, A>> for Pin<Box<T, A>>where
A: 'static + Allocator,
source§fn from(boxed: Box<T, A>) -> Self
fn from(boxed: Box<T, A>) -> Self
Converts a Box<T>
into a Pin<Box<T>>
. If T
does not implement Unpin
, then
*boxed
will be pinned in memory and unable to be moved.
This conversion does not allocate on the heap and happens in place.
This is also available via Box::into_pin
.
Constructing and pinning a Box
with <Pin<Box<T>>>::from(Box::new(x))
can also be written more concisely using Box::pin(x)
.
This From
implementation is useful if you already have a Box<T>
, or you are
constructing a (pinned) Box
in a different way than with Box::new
.
1.19.0 · source§impl<A: Allocator> From<Box<str, A>> for Box<[u8], A>
impl<A: Allocator> From<Box<str, A>> for Box<[u8], A>
source§fn from(s: Box<str, A>) -> Self
fn from(s: Box<str, A>) -> Self
Converts a Box<str>
into a Box<[u8]>
This conversion does not allocate on the heap and happens in place.
§Examples
// create a Box<str> which will be used to create a Box<[u8]>
let boxed: Box<str> = Box::from("hello");
let boxed_str: Box<[u8]> = Box::from(boxed);
// create a &[u8] which will be used to create a Box<[u8]>
let slice: &[u8] = &[104, 101, 108, 108, 111];
let boxed_slice = Box::from(slice);
assert_eq!(boxed_slice, boxed_str);
1.45.0 · source§impl From<Cow<'_, str>> for Box<str>
impl From<Cow<'_, str>> for Box<str>
source§fn from(cow: Cow<'_, str>) -> Box<str>
fn from(cow: Cow<'_, str>) -> Box<str>
Converts a Cow<'_, str>
into a Box<str>
When cow
is the Cow::Borrowed
variant, this
conversion allocates on the heap and copies the
underlying str
. Otherwise, it will try to reuse the owned
String
’s allocation.
§Examples
1.22.0 · source§impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + 'a>
impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + 'a>
1.22.0 · source§impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a>
impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a>
1.0.0 · source§impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a>
impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a>
source§fn from(err: E) -> Box<dyn Error + 'a>
fn from(err: E) -> Box<dyn Error + 'a>
Converts a type of Error
into a box of dyn Error
.
§Examples
use std::error::Error;
use std::fmt;
use std::mem;
#[derive(Debug)]
struct AnError;
impl fmt::Display for AnError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "An error")
}
}
impl Error for AnError {}
let an_error = AnError;
assert!(0 == mem::size_of_val(&an_error));
let a_boxed_error = Box::<dyn Error>::from(an_error);
assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
1.0.0 · source§impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a>
impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a>
source§fn from(err: E) -> Box<dyn Error + Send + Sync + 'a>
fn from(err: E) -> Box<dyn Error + Send + Sync + 'a>
Converts a type of Error
+ Send
+ Sync
into a box of
dyn Error
+ Send
+ Sync
.
§Examples
use std::error::Error;
use std::fmt;
use std::mem;
#[derive(Debug)]
struct AnError;
impl fmt::Display for AnError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "An error")
}
}
impl Error for AnError {}
unsafe impl Send for AnError {}
unsafe impl Sync for AnError {}
let an_error = AnError;
assert!(0 == mem::size_of_val(&an_error));
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(an_error);
assert!(
mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
1.6.0 · source§impl<'a> From<String> for Box<dyn Error + 'a>
impl<'a> From<String> for Box<dyn Error + 'a>
1.0.0 · source§impl<'a> From<String> for Box<dyn Error + Send + Sync + 'a>
impl<'a> From<String> for Box<dyn Error + Send + Sync + 'a>
1.20.0 · source§impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A>
impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A>
1.32.0 · source§impl<I> FromIterator<I> for Box<[I]>
impl<I> FromIterator<I> for Box<[I]>
source§fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self
fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self
1.22.0 · source§impl<T: ?Sized + Hasher, A: Allocator> Hasher for Box<T, A>
impl<T: ?Sized + Hasher, A: Allocator> Hasher for Box<T, A>
source§fn write_u128(&mut self, i: u128)
fn write_u128(&mut self, i: u128)
u128
into this hasher.source§fn write_usize(&mut self, i: usize)
fn write_usize(&mut self, i: usize)
usize
into this hasher.source§fn write_i128(&mut self, i: i128)
fn write_i128(&mut self, i: i128)
i128
into this hasher.source§fn write_isize(&mut self, i: isize)
fn write_isize(&mut self, i: isize)
isize
into this hasher.1.0.0 · source§impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A>
impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A>
source§fn next(&mut self) -> Option<I::Item>
fn next(&mut self) -> Option<I::Item>
source§fn size_hint(&self) -> (usize, Option<usize>)
fn size_hint(&self) -> (usize, Option<usize>)
source§fn nth(&mut self, n: usize) -> Option<I::Item>
fn nth(&mut self, n: usize) -> Option<I::Item>
n
th element of the iterator. Read moresource§fn next_chunk<const N: usize>(
&mut self,
) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>where
Self: Sized,
fn next_chunk<const N: usize>(
&mut self,
) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>where
Self: Sized,
iter_next_chunk
#98326)N
values. Read more1.0.0 · source§fn count(self) -> usizewhere
Self: Sized,
fn count(self) -> usizewhere
Self: Sized,
source§fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>>
fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>>
iter_advance_by
#77404)n
elements. Read more1.28.0 · source§fn step_by(self, step: usize) -> StepBy<Self>where
Self: Sized,
fn step_by(self, step: usize) -> StepBy<Self>where
Self: Sized,
1.0.0 · source§fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter>
fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter>
1.0.0 · source§fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter>where
Self: Sized,
U: IntoIterator,
fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter>where
Self: Sized,
U: IntoIterator,
source§fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>
fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>
iter_intersperse
#79524)separator
between adjacent items of the original iterator. Read more1.0.0 · source§fn map<B, F>(self, f: F) -> Map<Self, F>
fn map<B, F>(self, f: F) -> Map<Self, F>
1.0.0 · source§fn filter<P>(self, predicate: P) -> Filter<Self, P>
fn filter<P>(self, predicate: P) -> Filter<Self, P>
1.0.0 · source§fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>
fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>
1.0.0 · source§fn enumerate(self) -> Enumerate<Self>where
Self: Sized,
fn enumerate(self) -> Enumerate<Self>where
Self: Sized,
1.0.0 · source§fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>
fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>
1.0.0 · source§fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>
fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>
1.57.0 · source§fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P>
fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P>
1.0.0 · source§fn skip(self, n: usize) -> Skip<Self>where
Self: Sized,
fn skip(self, n: usize) -> Skip<Self>where
Self: Sized,
n
elements. Read more1.0.0 · source§fn take(self, n: usize) -> Take<Self>where
Self: Sized,
fn take(self, n: usize) -> Take<Self>where
Self: Sized,
n
elements, or fewer
if the underlying iterator ends sooner. Read more1.0.0 · source§fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>
fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>
source§fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N>
fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N>
iter_map_windows
#87155)f
for each contiguous window of size N
over
self
and returns an iterator over the outputs of f
. Like slice::windows()
,
the windows during mapping overlap as well. Read more1.0.0 · source§fn inspect<F>(self, f: F) -> Inspect<Self, F>
fn inspect<F>(self, f: F) -> Inspect<Self, F>
1.0.0 · source§fn by_ref(&mut self) -> &mut Selfwhere
Self: Sized,
fn by_ref(&mut self) -> &mut Selfwhere
Self: Sized,
source§fn collect_into<E>(self, collection: &mut E) -> &mut E
fn collect_into<E>(self, collection: &mut E) -> &mut E
iter_collect_into
#94780)1.0.0 · source§fn partition<B, F>(self, f: F) -> (B, B)
fn partition<B, F>(self, f: F) -> (B, B)
source§fn is_partitioned<P>(self, predicate: P) -> bool
fn is_partitioned<P>(self, predicate: P) -> bool
iter_is_partitioned
#62544)true
precede all those that return false
. Read more1.27.0 · source§fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
1.27.0 · source§fn try_for_each<F, R>(&mut self, f: F) -> R
fn try_for_each<F, R>(&mut self, f: F) -> R
1.0.0 · source§fn fold<B, F>(self, init: B, f: F) -> B
fn fold<B, F>(self, init: B, f: F) -> B
1.51.0 · source§fn reduce<F>(self, f: F) -> Option<Self::Item>
fn reduce<F>(self, f: F) -> Option<Self::Item>
source§fn try_reduce<R>(
&mut self,
f: impl FnMut(Self::Item, Self::Item) -> R,
) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType
fn try_reduce<R>( &mut self, f: impl FnMut(Self::Item, Self::Item) -> R, ) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType
iterator_try_reduce
#87053)1.0.0 · source§fn all<F>(&mut self, f: F) -> bool
fn all<F>(&mut self, f: F) -> bool
1.0.0 · source§fn any<F>(&mut self, f: F) -> bool
fn any<F>(&mut self, f: F) -> bool
1.0.0 · source§fn find<P>(&mut self, predicate: P) -> Option<Self::Item>
fn find<P>(&mut self, predicate: P) -> Option<Self::Item>
1.30.0 · source§fn find_map<B, F>(&mut self, f: F) -> Option<B>
fn find_map<B, F>(&mut self, f: F) -> Option<B>
source§fn try_find<R>(
&mut self,
f: impl FnMut(&Self::Item) -> R,
) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType
fn try_find<R>( &mut self, f: impl FnMut(&Self::Item) -> R, ) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType
try_find
#63178)1.0.0 · source§fn position<P>(&mut self, predicate: P) -> Option<usize>
fn position<P>(&mut self, predicate: P) -> Option<usize>
1.6.0 · source§fn max_by_key<B, F>(self, f: F) -> Option<Self::Item>
fn max_by_key<B, F>(self, f: F) -> Option<Self::Item>
1.15.0 · source§fn max_by<F>(self, compare: F) -> Option<Self::Item>
fn max_by<F>(self, compare: F) -> Option<Self::Item>
1.6.0 · source§fn min_by_key<B, F>(self, f: F) -> Option<Self::Item>
fn min_by_key<B, F>(self, f: F) -> Option<Self::Item>
1.15.0 · source§fn min_by<F>(self, compare: F) -> Option<Self::Item>
fn min_by<F>(self, compare: F) -> Option<Self::Item>
1.0.0 · source§fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)
fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)
1.36.0 · source§fn copied<'a, T>(self) -> Copied<Self>
fn copied<'a, T>(self) -> Copied<Self>
source§fn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N>where
Self: Sized,
fn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N>where
Self: Sized,
iter_array_chunks
#100450)N
elements of the iterator at a time. Read more1.11.0 · source§fn product<P>(self) -> P
fn product<P>(self) -> P
source§fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering
fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering
iter_order_by
#64295)Iterator
with those
of another with respect to the specified comparison function. Read more1.5.0 · source§fn partial_cmp<I>(self, other: I) -> Option<Ordering>
fn partial_cmp<I>(self, other: I) -> Option<Ordering>
PartialOrd
elements of
this Iterator
with those of another. The comparison works like short-circuit
evaluation, returning a result without comparing the remaining elements.
As soon as an order can be determined, the evaluation stops and a result is returned. Read moresource§fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>where
Self: Sized,
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>where
Self: Sized,
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
iter_order_by
#64295)Iterator
with those
of another with respect to the specified comparison function. Read moresource§fn eq_by<I, F>(self, other: I, eq: F) -> bool
fn eq_by<I, F>(self, other: I, eq: F) -> bool
iter_order_by
#64295)1.5.0 · source§fn lt<I>(self, other: I) -> bool
fn lt<I>(self, other: I) -> bool
Iterator
are lexicographically
less than those of another. Read more1.5.0 · source§fn le<I>(self, other: I) -> bool
fn le<I>(self, other: I) -> bool
Iterator
are lexicographically
less or equal to those of another. Read more1.5.0 · source§fn gt<I>(self, other: I) -> bool
fn gt<I>(self, other: I) -> bool
Iterator
are lexicographically
greater than those of another. Read more1.5.0 · source§fn ge<I>(self, other: I) -> bool
fn ge<I>(self, other: I) -> bool
Iterator
are lexicographically
greater than or equal to those of another. Read more1.82.0 · source§fn is_sorted_by<F>(self, compare: F) -> bool
fn is_sorted_by<F>(self, compare: F) -> bool
1.82.0 · source§fn is_sorted_by_key<F, K>(self, f: F) -> bool
fn is_sorted_by_key<F, K>(self, f: F) -> bool
1.0.0 · source§impl<T: ?Sized + Ord, A: Allocator> Ord for Box<T, A>
impl<T: ?Sized + Ord, A: Allocator> Ord for Box<T, A>
1.0.0 · source§impl<T: ?Sized + PartialOrd, A: Allocator> PartialOrd for Box<T, A>
impl<T: ?Sized + PartialOrd, A: Allocator> PartialOrd for Box<T, A>
1.43.0 · source§impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]>
impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]>
1.66.0 · source§impl<T, const N: usize> TryFrom<Vec<T>> for Box<[T; N]>
impl<T, const N: usize> TryFrom<Vec<T>> for Box<[T; N]>
source§fn try_from(vec: Vec<T>) -> Result<Self, Self::Error>
fn try_from(vec: Vec<T>) -> Result<Self, Self::Error>
Attempts to convert a Vec<T>
into a Box<[T; N]>
.
Like Vec::into_boxed_slice
, this is in-place if vec.capacity() == N
,
but will require a reallocation otherwise.
§Errors
Returns the original Vec<T>
in the Err
variant if
boxed_slice.len()
does not equal N
.
§Examples
This can be used with vec!
to create an array on the heap:
impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A>
impl<T: ?Sized, A: Allocator> DerefPure for Box<T, A>
impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Box<U>> for Box<T, Global>
impl<T: ?Sized + Eq, A: Allocator> Eq for Box<T, A>
impl<I: FusedIterator + ?Sized, A: Allocator> FusedIterator for Box<I, A>
impl<'a, I, A: Allocator> !Iterator for &'a Box<[I], A>
This implementation is required to make sure that the &Box<[I]>: IntoIterator
implementation doesn’t overlap with IntoIterator for T where T: Iterator
blanket.
impl<'a, I, A: Allocator> !Iterator for &'a mut Box<[I], A>
This implementation is required to make sure that the &mut Box<[I]>: IntoIterator
implementation doesn’t overlap with IntoIterator for T where T: Iterator
blanket.
impl<I, A: Allocator> !Iterator for Box<[I], A>
This implementation is required to make sure that the Box<[I]>: IntoIterator
implementation doesn’t overlap with IntoIterator for T where T: Iterator
blanket.
impl<T: ?Sized, A: Allocator> PinCoerceUnsized for Box<T, A>
impl<T: ?Sized, A: Allocator> Unpin for Box<T, A>
Auto Trait Implementations§
impl<T, A> Freeze for Box<T, A>
impl<T, A> RefUnwindSafe for Box<T, A>
impl<T, A> Send for Box<T, A>
impl<T, A> Sync for Box<T, A>
impl<T, A> UnwindSafe for Box<T, A>
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T> CloneToUninit for Twhere
T: Clone,
impl<T> CloneToUninit for Twhere
T: Clone,
source§impl<I> IntoAsyncIterator for Iwhere
I: AsyncIterator,
impl<I> IntoAsyncIterator for Iwhere
I: AsyncIterator,
source§type Item = <I as AsyncIterator>::Item
type Item = <I as AsyncIterator>::Item
async_iterator
#79024)source§type IntoAsyncIter = I
type IntoAsyncIter = I
async_iterator
#79024)source§fn into_async_iter(self) -> <I as IntoAsyncIterator>::IntoAsyncIter
fn into_async_iter(self) -> <I as IntoAsyncIterator>::IntoAsyncIter
async_iterator
#79024)self
into an async iteratorsource§impl<F> IntoFuture for Fwhere
F: Future,
impl<F> IntoFuture for Fwhere
F: Future,
source§type IntoFuture = F
type IntoFuture = F
source§fn into_future(self) -> <F as IntoFuture>::IntoFuture
fn into_future(self) -> <F as IntoFuture>::IntoFuture
source§impl<I> IntoIterator for Iwhere
I: Iterator,
impl<I> IntoIterator for Iwhere
I: Iterator,
source§impl<F> Pattern for F
impl<F> Pattern for F
source§type Searcher<'a> = CharPredicateSearcher<'a, F>
type Searcher<'a> = CharPredicateSearcher<'a, F>
pattern
#27721)source§fn into_searcher<'a>(self, haystack: &'a str) -> CharPredicateSearcher<'a, F>
fn into_searcher<'a>(self, haystack: &'a str) -> CharPredicateSearcher<'a, F>
pattern
#27721)self
and the haystack
to search in.source§fn is_contained_in<'a>(self, haystack: &'a str) -> bool
fn is_contained_in<'a>(self, haystack: &'a str) -> bool
pattern
#27721)source§fn is_prefix_of<'a>(self, haystack: &'a str) -> bool
fn is_prefix_of<'a>(self, haystack: &'a str) -> bool
pattern
#27721)source§fn strip_prefix_of<'a>(self, haystack: &'a str) -> Option<&'a str>
fn strip_prefix_of<'a>(self, haystack: &'a str) -> Option<&'a str>
pattern
#27721)source§fn is_suffix_of<'a>(self, haystack: &'a str) -> boolwhere
CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,
fn is_suffix_of<'a>(self, haystack: &'a str) -> boolwhere
CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,
pattern
#27721)source§fn strip_suffix_of<'a>(self, haystack: &'a str) -> Option<&'a str>where
CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,
fn strip_suffix_of<'a>(self, haystack: &'a str) -> Option<&'a str>where
CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,
pattern
#27721)