Trait druid::piet::cairo::glib::bitflags::_core::clone::Clone

1.0.0 · source ·

pub trait Clone: Sized {
    // Required method
    fn clone(&self) -> Self;

    // Provided method
    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)
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§

source

fn clone(&self) -> Self

Returns a copy of the value.

Examples

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

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

Provided Methods§

source

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.

Implementors§

Trait druid::piet::cairo::glib::bitflags::_core::clone::Clone

Required Methods§

fn clone(&self) -> Self

Provided Methods§

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

Implementors§

impl Clone for Code

impl Clone for druid::Color

impl Clone for druid::Cursor

impl Clone for Handled

impl Clone for InternalEvent

impl Clone for InternalLifeCycle

impl Clone for druid::Location

impl Clone for MouseButton

impl Clone for druid::PlatformError

impl Clone for RawMods

impl Clone for RawWindowHandle

impl Clone for SysMods

impl Clone for Target

impl Clone for druid::Value

impl Clone for WindowLevel

impl Clone for WindowSizePolicy

impl Clone for druid::WindowState

impl Clone for BarHeldState

impl Clone for BarHoveredState

impl Clone for ScrollbarsEnabled

impl Clone for druid::tests::helpers::Record

impl Clone for druid::text::Attribute

impl Clone for druid::text::Direction

impl Clone for druid::text::ImeInvalidation

impl Clone for Movement

impl Clone for druid::text::TextAction

impl Clone for VerticalMovement

impl Clone for WritingDirection

impl Clone for Axis

impl Clone for CrossAxisAlignment

impl Clone for FillStrat

impl Clone for KnobStyle

impl Clone for LineBreaking

impl Clone for MainAxisAlignment

impl Clone for TabsEdge

impl Clone for TabsTransition

impl Clone for druid::widget::prelude::Event

impl Clone for LifeCycle

impl Clone for ColorParseError

impl Clone for FixedGradient

impl Clone for FontStyle

impl Clone for druid::piet::ImageFormat

impl Clone for InterpolationMode

impl Clone for druid::piet::LineCap

impl Clone for druid::piet::LineJoin

impl Clone for PaintBrush

impl Clone for ScaleMode

impl Clone for TextAlignment

impl Clone for druid::piet::TextAttribute

impl Clone for druid::piet::image_crate::ColorType

impl Clone for DynamicImage

impl Clone for ExtendedColorType

impl Clone for druid::piet::image_crate::ImageFormat

impl Clone for ImageOutputFormat

impl Clone for ImageFormatHint

impl Clone for LimitErrorKind

impl Clone for ParameterErrorKind

impl Clone for UnsupportedErrorKind

impl Clone for druid::piet::image_crate::flat::Error

impl Clone for NormalForm

impl Clone for druid::piet::image_crate::imageops::FilterType

impl Clone for druid::piet::kurbo::PathEl

impl Clone for druid::piet::kurbo::PathSeg

impl Clone for Antialias

impl Clone for Content

impl Clone for druid::piet::cairo::DeviceType

impl Clone for druid::piet::cairo::Error

impl Clone for Extend

impl Clone for druid::piet::cairo::FillRule

impl Clone for druid::piet::cairo::Filter

impl Clone for FontSlant

impl Clone for FontType

impl Clone for druid::piet::cairo::FontWeight

impl Clone for druid::piet::cairo::Format