Observer 패턴 예제

Observer Interface

interface Observer {
    fun update()
}

Subject Interface

interface Subject {
    fun register(obj: Observer)
    fun unregister(obj: Observer)
    fun notifyObservers()
    fun getUpdate(obj: Observer): String
}

Topic Class

class Topic : Subject {

    private val observers: MutableSet<Observer> = mutableSetOf()
    private var message: String = ""

    override fun register(obj: Observer) {
        observers.add(obj)
    }

    override fun unregister(obj: Observer) {
        observers.remove(obj)
    }

    override fun notifyObservers() {
        observers.forEach(Observer::update)
    }

    override fun getUpdate(obj: Observer): String {
        return message
    }

    fun postMessage(message: String) {
        println("Enter the message: $message")
        this.message = message
        notifyObservers()
    }

}

TopicSubscriber Class

class TopicSubscriber(
    private val name: String,
    private val topic: Subject
) : Observer {

    override fun update() {
        val msg = topic.getUpdate(this)
        println("$name got notified about $msg")
    }
}

Main Kt

 

 

주제 서식자 클래스

fun main() {
    val topic = Topic()
    val a = TopicSubscriber("a", topic)
    val b = TopicSubscriber("b", topic)
    val c = TopicSubscriber("c", topic)
    topic.register(a)
    topic.register(b)
    topic.register(c)

    topic.postMessage("hello world!")
}

Output

소스코드

https://github.com/Kuass/KotlinObserverPattern 에서 확인 가능합니다.