Learning Concurrency in Kotlin

Creating an actor

Say that we need to modify a counter safely from many different threads. First, let's create a new class. In that class, we can have a private counter and a private single-thread dispatcher, with a function to retrieve the current value of the counter:

private var counter = 0private val context = newSingleThreadContext("counterActor")fun getCounter() = counter

Now that we have encapsulated the value of the counter, we simply need to add an actor that will increase the value upon each received message:

val actorCounter = actor<Void?>(context) {    for (msg in channel) {        counter++    }}

Because we don't actually use the message being sent, we can simply set the type of the actor to Void?, so that the caller can send null. Now we ...