final class Promise[E, A] extends Serializable

A promise represents an asynchronous variable, of zio.ZIO type, that can be set exactly once, with the ability for an arbitrary number of fibers to suspend (by calling await) and automatically resume when the variable is set.

Promises can be used for building primitive actions whose completions require the coordinated action of multiple fibers, and for building higher-level concurrent or asynchronous structures.

for {
  promise <- Promise.make[Nothing, Int]
  _       <- promise.succeed(42).delay(1.second).fork
  value   <- promise.await // Resumes when forked fiber completes promise
} yield value
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  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  4. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  5. def await(implicit trace: Trace): IO[E, A]

    Retrieves the value of the promise, suspending the fiber running the action until the result is available.

  6. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  7. def complete(io: IO[E, A])(implicit trace: Trace): UIO[Boolean]

    Completes the promise with the result of the specified effect.

    Completes the promise with the result of the specified effect. If the promise has already been completed, the method will produce false.

    Note that Promise.completeWith will be much faster, so consider using that if you do not need to memoize the result of the specified effect.

  8. def completeWith(io: IO[E, A])(implicit trace: Trace): UIO[Boolean]

    Completes the promise with the specified effect.

    Completes the promise with the specified effect. If the promise has already been completed, the method will produce false.

    Note that since the promise is completed with an effect, the effect will be evaluated each time the value of the promise is retrieved through combinators such as await, potentially producing different results if the effect produces different results on subsequent evaluations. In this case te meaning of the "exactly once" guarantee of Promise is that the promise can be completed with exactly one effect. For a version that completes the promise with the result of an effect see Promise.complete.

  9. def die(e: Throwable)(implicit trace: Trace): UIO[Boolean]

    Kills the promise with the specified error, which will be propagated to all fibers waiting on the value of the promise.

  10. def done(e: Exit[E, A])(implicit trace: Trace): UIO[Boolean]

    Exits the promise with the specified exit, which will be propagated to all fibers waiting on the value of the promise.

  11. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  12. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  13. def fail(e: E)(implicit trace: Trace): UIO[Boolean]

    Fails the promise with the specified error, which will be propagated to all fibers waiting on the value of the promise.

  14. def failCause(e: Cause[E])(implicit trace: Trace): UIO[Boolean]

    Fails the promise with the specified cause, which will be propagated to all fibers waiting on the value of the promise.

  15. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  16. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  17. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  18. def interrupt(implicit trace: Trace): UIO[Boolean]

    Completes the promise with interruption.

    Completes the promise with interruption. This will interrupt all fibers waiting on the value of the promise as by the fiber calling this method.

  19. def interruptAs(fiberId: FiberId)(implicit trace: Trace): UIO[Boolean]

    Completes the promise with interruption.

    Completes the promise with interruption. This will interrupt all fibers waiting on the value of the promise as by the specified fiber.

  20. def isDone(implicit trace: Trace): UIO[Boolean]

    Checks for completion of this Promise.

    Checks for completion of this Promise. Produces true if this promise has already been completed with a value or an error and false otherwise.

  21. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  22. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  23. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  24. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  25. def poll(implicit trace: Trace): UIO[Option[IO[E, A]]]

    Checks for completion of this Promise.

    Checks for completion of this Promise. Returns the result effect if this promise has already been completed or a None otherwise.

  26. def refailCause(e: Cause[E])(implicit trace: Trace): UIO[Boolean]

    Fails the promise with the specified cause, which will be propagated to all fibers waiting on the value of the promise.

    Fails the promise with the specified cause, which will be propagated to all fibers waiting on the value of the promise. No new stack trace is attached to the cause.

  27. def succeed(a: A)(implicit trace: Trace): UIO[Boolean]

    Completes the promise with the specified value.

  28. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  29. def toString(): String
    Definition Classes
    AnyRef → Any
  30. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  31. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  32. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()

Inherited from Serializable

Inherited from Serializable

Inherited from AnyRef

Inherited from Any

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