1.0.0[−][src]Trait core::clone::Clone

#[lang = "clone"]pub trait Clone: Sized {
#[must_use =
  "cloning is often expensive and is not expected to have side effects"]    pub fn clone(&self) -> Self;

    pub fn clone_from(&mut self, source: &Self) { ... }
}

A common trait for the ability to explicitly duplicate an object.

Differs from Copy in that Copy is implicit and extremely inexpensive, while Clone is always explicit and may or may not be expensive. In order to enforce these characteristics, Rust does not allow you to reimplement Copy, but you may reimplement Clone and run arbitrary code.

Since Clone is more general than Copy, you can automatically make anything Copy be Clone as well.

Derivable

This trait can be used with #[derive] if all fields are Clone. The derived implementation of Clone calls clone on each field.

For a generic struct, #[derive] implements Clone conditionally by adding bound Clone on generic parameters.

// `derive` implements Clone for Reading<T> when T is Clone.
#[derive(Clone)]
struct Reading<T> {
    frequency: T,
}

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How can I implement `Clone`?

Types that are Copy should have a trivial implementation of Clone. More formally: if T: Copy, x: T, and y: &T, then let x = y.clone(); is equivalent to let x = *y;. Manual implementations should be careful to uphold this invariant; however, unsafe code must not rely on it to ensure memory safety.

An example is a generic struct holding a function pointer. In this case, the implementation of Clone cannot be derived, but can be implemented as:

struct Generate<T>(fn() -> T);

impl<T> Copy for Generate<T> {}

impl<T> Clone for Generate<T> {
    fn clone(&self) -> Self {
        *self
    }
}

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Additional implementors

In addition to the implementors listed below, the following types also implement Clone:

Function item types (i.e., the distinct types defined for each function)
Function pointer types (e.g., fn() -> i32)
Array types, for all sizes, if the item type also implements Clone (e.g., [i32; 123456])
Tuple types, if each component also implements Clone (e.g., (), (i32, bool))
Closure types, if they capture no value from the environment or if all such captured values implement Clone themselves. Note that variables captured by shared reference always implement Clone (even if the referent doesn't), while variables captured by mutable reference never implement Clone.

Required methods

`#[must_use = "cloning is often expensive and is not expected to have side effects"]pub fn clone(&self) -> Self`[src]

Returns a copy of the value.

Examples

let hello = "Hello"; // &str implements Clone

assert_eq!("Hello", hello.clone());

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Provided methods

`pub fn clone_from(&mut self, source: &Self)`[src]

Performs copy-assignment from source.

a.clone_from(&b) is equivalent to a = b.clone() in functionality, but can be overridden to reuse the resources of a to avoid unnecessary allocations.

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Implementors

`impl Clone for !`[src]

`pub fn clone(&self) -> Self`[src]

`impl Clone for core::cmp::Ordering`[src]

`pub fn clone(&self) -> Ordering`[src]

`impl Clone for Infallible`[src]

`pub fn clone(&self) -> Infallible`[src]

`impl Clone for FpCategory`[src]

`pub fn clone(&self) -> FpCategory`[src]

`impl Clone for IntErrorKind`[src]

`pub fn clone(&self) -> IntErrorKind`[src]

`impl Clone for SearchStep`[src]

`pub fn clone(&self) -> SearchStep`[src]

`impl Clone for core::sync::atomic::Ordering`[src]

`pub fn clone(&self) -> Ordering`[src]

`impl Clone for AllocError`[src]

`pub fn clone(&self) -> AllocError`[src]

`impl Clone for Layout`[src]

`pub fn clone(&self) -> Layout`[src]

`impl Clone for LayoutError`[src]

`pub fn clone(&self) -> LayoutError`[src]

`impl Clone for TypeId`[src]

`pub fn clone(&self) -> TypeId`[src]

`impl Clone for float64x1_t`[src]

This is supported on AArch64 only.

`pub fn clone(&self) -> float64x1_t`[src]

`impl Clone for float64x2_t`[src]

This is supported on AArch64 only.

`pub fn clone(&self) -> float64x2_t`[src]

`impl Clone for int8x16x2_t`[src]

This is supported on AArch64 only.

`pub fn clone(&self) -> int8x16x2_t`[src]

`impl Clone for int8x16x3_t`[src]

This is supported on AArch64 only.

`pub fn clone(&self) -> int8x16x3_t`[src]

`impl Clone for int8x16x4_t`[src]

This is supported on AArch64 only.

`pub fn clone(&self) -> int8x16x4_t`[src]

`impl Clone for poly8x16x2_t`[src]

This is supported on AArch64 only.

`pub fn clone(&self) -> poly8x16x2_t`[src]

`impl Clone for poly8x16x3_t`[src]

This is supported on AArch64 only.

`pub fn clone(&self) -> poly8x16x3_t`[src]

`impl Clone for poly8x16x4_t`[src]

This is supported on AArch64 only.

`pub fn clone(&self) -> poly8x16x4_t`[src]

`impl Clone for uint8x16x2_t`[src]

This is supported on AArch64 only.

`pub fn clone(&self) -> uint8x16x2_t`[src]

`impl Clone for uint8x16x3_t`[src]

This is supported on AArch64 only.

`pub fn clone(&self) -> uint8x16x3_t`[src]