C#-style events in Kotlin

event.kt

class Event<T> {
    private val handlers = arrayListOf<(T) -> Unit>()
    operator fun plusAssign(handler: (T) -> Unit) { handlers.add(handler) }
    operator fun invoke(value: T) { for (handler in handlers) handler(value) }
}

val e = Event<String>() // define event

fun main(args : Array<String>) {
    e += { println(it) } // subscribe
    e("sdfsdf") // invoke
}

A shorter version that also reduces the visibility problem, at least for code outside of the module:

class Event<TArgs> : ArrayList<(TArgs) -> Unit>() {
    internal operator fun invoke(e: TArgs) = forEach { it(e) }
}