pub struct LocalKey<T: 'static> { /* private fields */ }
This is supported on crate feature rt only.
Expand description

A key for task-local data.

This type is generated by the task_local! macro.

Unlike std::thread::LocalKey, tokio::task::LocalKey will not lazily initialize the value on first access. Instead, the value is first initialized when the future containing the task-local is first polled by a futures executor, like Tokio.

Examples

tokio::task_local! {
    static NUMBER: u32;
}

NUMBER.scope(1, async move {
    assert_eq!(NUMBER.get(), 1);
}).await;

NUMBER.scope(2, async move {
    assert_eq!(NUMBER.get(), 2);

    NUMBER.scope(3, async move {
        assert_eq!(NUMBER.get(), 3);
    }).await;
}).await;

Implementations

Sets a value T as the task-local value for the future F.

On completion of scope, the task-local will be dropped.

Examples
tokio::task_local! {
    static NUMBER: u32;
}

NUMBER.scope(1, async move {
    println!("task local value: {}", NUMBER.get());
}).await;

Sets a value T as the task-local value for the closure F.

On completion of scope, the task-local will be dropped.

Examples
tokio::task_local! {
    static NUMBER: u32;
}

NUMBER.sync_scope(1, || {
    println!("task local value: {}", NUMBER.get());
});

Accesses the current task-local and runs the provided closure.

Panics

This function will panic if not called within the context of a future containing a task-local with the corresponding key.

Accesses the current task-local and runs the provided closure.

If the task-local with the associated key is not present, this method will return an AccessError. For a panicking variant, see with.

Returns a copy of the task-local value if the task-local value implements Copy.

Trait Implementations

Formats the value using the given formatter. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Performs the conversion.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.