CODEWITHSUNDEEP
scalafuturetraits
Mandroid
Mandroid

Reputation: 7478

Implementation of Future's isCompleted method?

In following code:

val sbtFile: Future[String] = Future{
  val f = Source.fromFile("build.sbt")
  try f.getLines.mkString("\n") finally f.close()
}
println(s"status: ${sbtFile.isCompleted}")
Thread.sleep(250)
println(s"status: ${sbtFile.isCompleted}")
println(s"value: ${sbtFile.value}")

Future trait has polling method:isCompleted. This method is being called in above code.

In trait Future,this method is:

abstract def isCompleted: Boolean

Also, there is an object,never,defined in Future companion object and it extends Future trait,and returns false for isCompleted.

I couldn't find any other implementation.

So, which concrete completion is being called here?

Upvotes: 0

Views: 369

Answers (1)

Denis Makarenko
Denis Makarenko

Reputation: 2938

In IntelliJ, right click on the isCompleted in your code and then Go To > Implementations. One of the places displayed will be scala.concurrent.impl.Promise as @Antot mentioned in the comment:

 class DefaultPromise[T] extends AtomicReference[AnyRef](Nil) with Promise[T] {
// ...
   override final def isCompleted: Boolean = isCompleted0
// ...
}

Upvotes: 1

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