Struct pawawwewism::PromiseHandle

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

A handle connected to a Promise that will eventually resolve to a value of type T.

A connected pair of Promise and PromiseHandle can be created by calling promise.

Implementations

impl<T> PromiseHandle<T>

pub fn block(self) -> Result<T, PromiseDropped>

Blocks the calling thread until the connected Promise is fulfilled.

If the Promise is dropped without being fulfilled, a PromiseDropped error is returned instead. This typically means one of two things:

• The thread holding the promise has deliberately decided not to fulfill it (for example, because it has skipped processing an item).
• The thread holding the promise has panicked.

Usually, the correct way to handle this is to just skip the item expected from the Promise. If the thread has panicked, and it’s a Worker thread, then the next attempt to send a message to it will propagate the panic to the owning thread, and tear down the process as usual.

pub async fn wait(self) -> Result<T, PromiseDropped>

Asynchronously waits for the connected Promise to be fulfilled.

Cancellation

This method is cancellation-safe, but it takes self by value, so the value of the Promise will be lost when the resulting Future is cancelled.

pub fn will_block(&self) -> bool

Tests whether a call to PromiseHandle::block will block or return immediately.

If this returns false, the connected Promise has been resolved and calling PromiseHandle::block on self will return immediately, without blocking.