Struct futures::task::LocalKey
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[src]
pub struct LocalKey<T> { /* fields omitted */ }A key for task-local data stored in a future's task.
This type is generated by the task_local! macro and performs very
similarly to the thread_local! macro and std::thread::LocalKey types.
Data associated with a LocalKey<T> is stored inside of a future's task,
and the data is destroyed when the future is completed and the task is
destroyed.
Task-local data can migrate between threads and hence requires a Send
bound. Additionally, task-local data also requires the 'static bound to
ensure it lives long enough. When a key is accessed for the first time the
task's data is initialized with the provided initialization expression to
the macro.
Methods
impl<T: Send + 'static> LocalKey<T>[src]
fn with<F, R>(&'static self, f: F) -> R where F: FnOnce(&T) -> R
Access this task-local key, running the provided closure with a reference to the value.
This function will access this task-local key to retrieve the data
associated with the current task and this key. If this is the first time
this key has been accessed on this task, then the key will be
initialized with the initialization expression provided at the time the
task_local! macro was called.
The provided closure will be provided a shared reference to the underlying data associated with this task-local-key. The data itself is stored inside of the current task.
Panics
This function can possibly panic for a number of reasons:
- If there is not a current task.
- If the initialization expression is run and it panics
- If the closure provided panics