Trait frame_support::dispatch::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.

Trait frame_support::dispatch::Clone

Required Methods§

fn clone(&self) -> Self

Provided Methods§

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

Implementors§

impl Clone for ArithmeticError

impl Clone for Rounding

impl Clone for SignedRounding

impl Clone for DeriveError

impl Clone for DeriveJunction

impl Clone for PublicError

impl Clone for SecretStringError

impl Clone for LogLevel

impl Clone for LogLevelFilter

impl Clone for Void

impl Clone for HttpError

impl Clone for HttpRequestStatus

impl Clone for OffchainOverlayedChange

impl Clone for StorageKind

impl Clone for CallContext

impl Clone for StorageEntryModifierIR

impl Clone for StorageHasherIR

impl Clone for MultiSignature

impl Clone for MultiSigner

impl Clone for TokenError

impl Clone for TransactionalError

impl Clone for DigestItem

impl Clone for Era

impl Clone for sp_runtime::legacy::byte_sized_error::DispatchError

impl Clone for sp_runtime::offchain::http::Error

impl Clone for Method

impl Clone for RuntimeString

impl Clone for DisableStrategy

impl Clone for BackendTrustLevel

impl Clone for IndexOperation

impl Clone for WasmLevel

impl Clone for WasmValue

impl Clone for sp_version::embed::Error

impl Clone for ReturnValue

impl Clone for sp_wasm_interface::Value

impl Clone for sp_wasm_interface::ValueType

impl Clone for Never

impl Clone for frame_support::pallet_prelude::DispatchError

impl Clone for InvalidTransaction

impl Clone for TransactionSource

impl Clone for TransactionValidityError

impl Clone for UnknownTransaction

impl Clone for ChildInfo

impl Clone for ChildType

impl Clone for StateVersion

impl Clone for ProcessMessageError

impl Clone for frame_support::traits::TryStateSelect

impl Clone for UpgradeCheckSelect

impl Clone for frame_support::traits::schedule::LookupError

impl Clone for BalanceStatus

impl Clone for DepositConsequence

impl Clone for ExistenceRequirement

impl Clone for Fortitude

impl Clone for Precision

impl Clone for Preservation

impl Clone for Provenance

impl Clone for Restriction

impl Clone for PaymentStatus

impl Clone for DispatchClass

impl Clone for Pays

impl Clone for frame_support::dispatch::fmt::Alignment

impl Clone for TryReserveErrorKind

impl Clone for core::cmp::Ordering

impl Clone for Infallible

impl Clone for Which

impl Clone for IpAddr

impl Clone for Ipv6MulticastScope

impl Clone for core::net::socket_addr::SocketAddr

impl Clone for FpCategory

impl Clone for IntErrorKind

impl Clone for SearchStep

impl Clone for core::sync::atomic::Ordering

impl Clone for proc_macro::diagnostic::Level

impl Clone for proc_macro::Delimiter