Struct may::LocalKey

pub struct LocalKey<T> { /* private fields */ }

A key for local data stored in a coroutine.

This type is generated by the coroutine_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 coroutine, and the data is destroyed when the coroutine is completed.

coroutine-local data requires the 'static bound to ensure it lives long enough. When a key is accessed for the first time the coroutine’s data is initialized with the provided initialization expression to the macro.

Implementations

impl<T: 'static> LocalKey<T>

pub fn with<F, R>(&'static self, f: F) -> R

where F: FnOnce(&T) -> R,

Access this coroutine-local key, running the provided closure with a reference to the value.

This function will access this coroutine-local key to retrieve the data associated with the current coroutine and this key. If this is the first time this key has been accessed on this coroutine, then the key will be initialized with the initialization expression provided at the time the coroutine_local! macro was called.

The provided closure will be provided a shared reference to the underlying data associated with this coroutine-local-key. The data itself is stored inside of the current coroutine.

if it’s not accessed in a coroutine context, it will use the thread local storage as a backend, so it’s safe to use it in thread context

Panics

This function can possibly panic for a number of reasons:

• If the initialization expression is run and it panics
• If the closure provided panics