arrow-fx / arrow.fx / Promise / tryComplete

tryComplete

abstract fun tryComplete(a: A): Kind<F, Boolean>

Try to complete, or fulfill, the promise with the specified value A. Returns true if the promise successfully completed, false otherwise.

import arrow.fx.*
import arrow.fx.extensions.io.async.async
import arrow.fx.extensions.io.monad.flatMap

fun main(args: Array<String>) {
  //sampleStart
  val promise = Promise.uncancellable<ForIO, Int>(IO.async())

  promise.flatMap { p ->
    p.tryComplete(1)
  }.unsafeRunSync() == true

  promise.flatMap { p ->
    p.complete(1).flatMap {
      p.tryComplete(2)
    }
  }.unsafeRunSync() == false
  //sampleEnd
}