Trait sp_std::convert::Into

pub trait Into<T> {
    fn into(self) -> T;
}

A value-to-value conversion that consumes the input value. The opposite of From.

One should avoid implementing Into and implement From instead. Implementing From automatically provides one with an implementation of Into thanks to the blanket implementation in the standard library.

Prefer using Into over From when specifying trait bounds on a generic function to ensure that types that only implement Into can be used as well.

Note: This trait must not fail. If the conversion can fail, use TryInto.

Generic Implementations

• From<T> for U implies Into<U> for T
• Into is reflexive, which means that Into<T> for T is implemented

Implementing Into for conversions to external types in old versions of Rust

Prior to Rust 1.41, if the destination type was not part of the current crate then you couldn’t implement From directly. For example, take this code:

struct Wrapper<T>(Vec<T>);
impl<T> From<Wrapper<T>> for Vec<T> {
    fn from(w: Wrapper<T>) -> Vec<T> {
        w.0
    }
}

This will fail to compile in older versions of the language because Rust’s orphaning rules used to be a little bit more strict. To bypass this, you could implement Into directly:

struct Wrapper<T>(Vec<T>);
impl<T> Into<Vec<T>> for Wrapper<T> {
    fn into(self) -> Vec<T> {
        self.0
    }
}

It is important to understand that Into does not provide a From implementation (as From does with Into). Therefore, you should always try to implement From and then fall back to Into if From can’t be implemented.

Examples

String implements Into<Vec<u8>>:

In order to express that we want a generic function to take all arguments that can be converted to a specified type T, we can use a trait bound of Into<T>. For example: The function is_hello takes all arguments that can be converted into a Vec<u8>.

fn is_hello<T: Into<Vec<u8>>>(s: T) {
   let bytes = b"hello".to_vec();
   assert_eq!(bytes, s.into());
}

let s = "hello".to_string();
is_hello(s);

Required methods

fn into(self) -> T

Performs the conversion.

Implementations on Foreign Types

impl Into<ExitStatus> for ExitStatusError

pub fn into(self) -> ExitStatus

Implementors

impl<T, U> Into<U> for T where
    U: From<T>, 

impl Into<OpaqueMetadata> for RuntimeMetadataPrefixed

impl Into<RuntimeMetadataPrefixed> for RuntimeMetadataLastVersion

impl Into<WasmExecutionMethod> for WasmExecutionMethod

impl Into<TracingReceiver> for TracingReceiver

impl Into<ExecutionStrategy> for ExecutionStrategy

impl Into<RpcMethods> for RpcMethods

impl Into<SyncMode> for SyncMode

impl Into<Arc<dyn SyncCryptoStore + 'static>> for LocalKeystore

impl Into<Arc<dyn CryptoStore + 'static>> for LocalKeystore

impl<'a> Into<Vec<(Public, u64), Global>> for VersionedAuthorityList<'a>

impl Into<Arc<dyn SyncCryptoStore + 'static>> for KeyStore

impl Into<Arc<dyn CryptoStore + 'static>> for KeyStore

impl Into<Result<RawOrigin<<Runtime as Config>::AccountId>, Origin>> for Origin