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C#-style events in Kotlin
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class Event<T> { | |
private val handlers = arrayListOf<(Event<T>.(T) -> Unit)>() | |
fun plusAssign(handler: Event<T>.(T) -> Unit) { handlers.add(handler) } | |
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 | |
} |
onTalk is null when Duck init at C#, but kotlin not support ref
keyword.
class Delegate<TS, TA> : Event<TS, TA> {
private var invocationList: MutableList<(TS, TA) -> Unit>? = null
override operator fun plusAssign(m: (TS, TA) -> Unit) {
val list = invocationList ?: mutableListOf<(TS, TA) -> Unit>().apply { invocationList = this }
list.add(m)
}
override operator fun minusAssign(m: (TS, TA) -> Unit) {
val list = invocationList
if (list != null) {
list.remove(m)
if (list.isEmpty()) {
invocationList = null
}
}
}
operator fun invoke(source: TS, arg: TA) {
val list = invocationList
if (list != null) {
for (m in list)
m(source, arg)
}
}
}
interface Event<out TS, out TA> {
operator fun plusAssign(m: (TS,TA) -> Unit)
operator fun minusAssign(m: (TS,TA) -> Unit)
}
class Duck {
private val onTalk = Delegate<Duck, String>()
val talking : Event<Duck,String> get() = onTalk
fun poke() {
onTalk(this, "Quaak!")
}
}
fun main(args: Array<String>) {
val duck = Duck()
duck.talking += fun(s: Duck, a: String ) { println("${s.javaClass.name}: $a")}
duck.poke()
}
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If use interface for event?