Struct ShardLocal 

pub struct ShardLocal<T: Send + 'static> { /* private fields */ }

A value per worker shard, declared with shard_local!.

Each worker of each runtime has its own value, made by the declaration’s expression the first time code running on that worker uses it, and dropped with the worker’s shard. Only code running on a worker (its tasks, and block_on called from them) reaches a value: a thread’s own shard in block_on, the blocking pool and any other thread have none.

A task spawned on a worker stays on that worker’s shard, and a handoff moves the shard with its values, so the task always sees one value. A task kept on a thread by spawn_local whose worker’s shard was handed on runs on that thread’s own shard, off the worker: it gets ShardAccessError there.

Implementations

impl<T: Send + 'static> ShardLocal<T>

pub fn with<R>(&'static self, f: impl FnOnce(&T) -> R) -> R

Runs f on this worker’s value, made now if this is its first use here.

While f runs the shard stays on this thread, even across a block_on inside f: keep f short, as a blocking f holds the whole worker up.

Panics

Off a worker, or when the value’s own initializer uses it; try_with answers the error instead.

pub fn try_with<R>( &'static self, f: impl FnOnce(&T) -> R, ) -> Result<R, ShardAccessError>

Runs f on this worker’s value, as with does, or answers a ShardAccessError off a worker or while the value’s own initializer runs.

Trait Implementations

impl<T: Send + 'static> Debug for ShardLocal<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.