A purely functional synchronization primitive which represents a single value which may not yet be available.
When created, a Deferred is empty. It can then be completed exactly once,
and never be made empty again.
get on an empty Deferred will block until the Deferred is completed.
get on a completed Deferred will always immediately return its content.
complete(a) on an empty Deferred will set it to a, notify any and
all readers currently blocked on a call to get, and return true.
complete(a) on a Deferred that has already been completed will not modify
its content, and return false.
Albeit simple, Deferred can 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.
- Companion
- object
Value members
Concrete methods
Inherited methods
If this Deferred is empty, sets the current value to a, and notifies
any and all readers currently blocked on a get. Returns true.
If this Deferred is empty, sets the current value to a, and notifies
any and all readers currently blocked on a get. Returns true.
If this Deferred has already been completed, returns false.
Satisfies:
Deferred[F, A].flatMap(r => r.complete(a) *> r.get) == a.pure[F]
- Inherited from
- DeferredSink
Obtains the value of the Deferred, or waits until it has been completed.
The returned value may be canceled.
Obtains the value of the Deferred, or waits until it has been completed.
The returned value may be canceled.
- Inherited from
- DeferredSource
Obtains the current value of the Deferred, or None if it hasn't completed.
Obtains the current value of the Deferred, or None if it hasn't completed.
- Inherited from
- DeferredSource