Trait std::clone::Clone 1.0.0[−][src]
pub trait Clone {
fn clone(&self) -> Self;
fn clone_from(&mut self, source: &Self) { ... }
}Expand description
A common trait for the ability to explicitly duplicate an object.
Differs from Copy in that Copy is implicit and an inexpensive bit-wise copy, 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,
}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
}
}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
Clonethemselves. Note that variables captured by shared reference always implementClone(even if the referent doesn’t), while variables captured by mutable reference never implementClone.
Required methods
Provided methods
fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
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.
Implementations on Foreign Types
pub fn clone(&self) -> SplitInclusive<'_, T, P>ⓘNotable traits for SplitInclusive<'a, T, P>impl<'a, T, P> Iterator for SplitInclusive<'a, T, P> where
P: FnMut(&T) -> bool, type Item = &'a [T];
impl<'a, T, P> Iterator for SplitInclusive<'a, T, P> where
P: FnMut(&T) -> bool, type Item = &'a [T];pub fn clone(&self) -> EscapeAscii<'a>ⓘNotable traits for EscapeAscii<'a>impl<'a> Iterator for EscapeAscii<'a> type Item = u8;
impl<'a> Iterator for EscapeAscii<'a> type Item = u8;