Handling callback on futures

In this recipe, you will learn how to handle future responses with callback functions; it is also known as asynchronous handling of futures. Using the callback function, we don't block the current thread for response from a future.

Getting ready

To step through this recipe, we will need to import the Hello-Akka project in the IDE, and the rest of the prerequisites are same as earlier.

How to do it...

1. Create a scala file, callback.scala, in the com.packt.chapter4 package.
2. Add the following import to the top of the file:

        import scala.concurrent.ExecutionContext.Implicits.global 
        import scala.concurrent.Future 
        import scala.util.{Failure, Success} 

3. Create a Scala application, as follows:

        object Callback extends App { 
          val future = Future(1 + 2).mapTo[Int] 
          future onComplete { 
            case Success(result) => println(s"result is $result") 
            case Failure(fail) => fail.printStackTrace() 
            ...