Kotlin: How to run a function with delay using extension function

Question

I'm trying to figure out how to use an extension function to run any method with a delay, but can't seem to figure it out.

I am trying something like below where I have a function and I want a handler to delay the execution by a certain timeInterval:

functionX().withDelay(500)
functionY().withDelay(500)

private fun Unit.withDelay(delay: Int) {
  Handler().postDelayed( {this} , delay)}

private fun Handler.postDelayed(function: () -> Any, delay: Int) {
  this.postDelayed(function, delay)}

Anyone?

Answer 1

Another approach would be to declare a top-level (i.e. global) function like this:

fun withDelay(delay : Long, block : () -> Unit) {
    Handler().postDelayed(Runnable(block), delay)
}

Then you can call it, from anywhere, like this:

withDelay(500) { functionX() }

Answer 2

You should put the extension on the function type, not Unit:

fun functionX() {}
fun functionY() {}

private fun (() -> Any).withDelay(delay: Int) {
     Handler().postDelayed(this , delay)
}

Usage:

::functionX.withDelay(500)
::functionY.withDelay(500)

Here, ::functionX is a reference to the global function called functionX.