Deferred
Related Docs:
object Deferred
| package concurrent
If this Deferred is empty, sets the current value to a, and notifies
any and all readers currently blocked on a get.
If this Deferred is empty, sets the current value to a, and notifies
any and all readers currently blocked on a get.
Note that the returned action may complete after the reference
has been successfully set: use F.start(r.complete) if you want
asynchronous behaviour.
If this Deferred has already been completed, the returned
action immediately fails with an IllegalStateException. In the
uncommon scenario where this behavior is problematic, you can
handle failure explicitly using attempt or any other
ApplicativeError/MonadError combinator on the returned
action.
Satisfies:
Deferred[F, A].flatMap(r => r.complete(a) *> r.get) == a.pure[F]
Obtains the value of the Deferred, or waits until it has been completed.
Obtains the value of the Deferred, or waits until it has been completed.
The returned value may be canceled.
Modify the context F using transformation f.
A purely functional synchronization primitive which represents a single value which may not yet be available.
When created, a
Deferredis empty. It can then be completed exactly once, and never be made empty again.geton an emptyDeferredwill block until theDeferredis completed.geton a completedDeferredwill always immediately return its content.complete(a)on an emptyDeferredwill set it toa, and notify any and all readers currently blocked on a call toget.complete(a)on aDeferredthat has already been completed will not modify its content, and result in a failedF.Albeit simple,
Deferredcan be used in conjunction with Ref to build complex concurrent behaviour and data structures like queues and semaphores.Finally, the blocking mentioned above is semantic only, no actual threads are blocked by the implementation.