Scala Future API callbacks

So far, we have demonstrated some of the useful ways to create a Scala Future and a Promise and displayed the results, using plain println statements. It's for understanding purposes only. In real-time projects, we don't use this approach.

We use the Scala Future API callback methods to check the following things from a Future object or a Promise object:

• Whether it is completed with a success result
• Whether it is completed with a failure
• Whether it is completed successfully or not completed

We use the following functions to check the preceding things, respectively:

• onSuccess (deprecated from Scala 2.12.0 onwards)
• onFailure (deprecated from Scala 2.12.0 onwards)
• onComplete

This example is about how to use a Scala Future's onComplete callback function. It refers to the scala.util.Try construct to check the Future value or exception. If you are new to this construct, refer to Chapter 2, Functional Scala, for more information. Let's explore Scala Future's onComplete() callback...