观察者模式Kotlin泛型实现消息中心

观察者模式 + Kotlin 泛型实现的简易版消息中心

class MessageCenter<T> {
  companion object {
    private val centers = mutableMapOf<String, Any>()
    fun <T> getInstance(clazz: Class<T>): MessageCenter<T> {
      return if (centers[clazz.simpleName] != null) {
        centers[clazz.simpleName] as MessageCenter<T>
      } else {
        val messageCenter = MessageCenter<T>()
        centers[clazz.simpleName] = messageCenter
        messageCenter
      }
    }
  }

  fun register(observer: Observer<T>) {
    observers.add(observer)
  }

  fun unregister(observer: Observer<T>) {
    if (observers.contains(observer)) {
      observers.remove(observer)
    }
  }

  fun post(t: T) {
    observers.forEach {
      it.receive(t)
    }
  }

  private var observers = mutableListOf<Observer<T>>()
}

interface Observer<T> {
  fun receive(t: T)
}

fun main() {
  val ob = object : Observer<String> {
    override fun receive(t: String) {
      println("result is: $t")
    }
  }
  MessageCenter.getInstance(String::class.java).register(ob)
  MessageCenter.getInstance(String::class.java).post("txt post.")
  MessageCenter.getInstance(String::class.java).unregister(ob)

  MessageCenter.getInstance(Int::class.java).post(123)
}