vertx-lang-kotlin | Vertx for Kotlin | Reactive Programming library

The compiler doesn't tell you the member is not initialized, it's telling you that you are not allowed to call functions in the class body without them being part of a member declaration.

e.g.

It seems the latest way of doing this is:

The whole point of Kotlin integration with Vert.x is that you don't have to use GlobalScope.launch

Here's a minimal example of how it can be achieved:

Many asynchronous operations in Vert.x take a Handler as the last argument. vertx.setTimer() is one of such asynchronous functions, it calls handler when the timer fires. According to the docs of Vertx.setTimer() method it accepts handler: Handler as the second parameter. We can conclude that generic type of Handler is Long.

Suspend function awaitEvent takes lambda block as the parameter, which in turn receives parameter of type Handler. According to the docs:

The block is executed with a Handler argument that shall be called once. When the handler is called, awaitEvent returns the value that the handler received.

So when passing handler to vertx.setTimer(1000, handler) function, it calls handler after the delay (1000 milliseconds) is elapsed and awaitEvent function in turn returns the value received by the handler (timer ID).