scala - Scala ObservableSet Trait 的使用示例

Question

谁能帮我告诉我如何使用scala的 ObservableSet 特征？

非常感谢您提前

Answer 1

ObservableSet是从 Publisher 延伸的特征trait，提供一些基本的发布订阅行为。使用它的一个简单示例是:

scala> class Counter(var count: Int) extends Publisher[String] {
          def inc(): Unit = {
              count += 1
              super.publish("updated count to: " + count)
          }
     }

scala> class S[Evt, Pub] extends Subscriber[Evt, Pub] {
         def notify(pub: Pub, event: Evt): Unit = println("got event: " + event)
      }
defined class S

scala> val s = new S[String, Counter#Pub]     
s: S[String,Counter#Pub] = S@7c27a30c

scala> val c = new Counter(1)
c: Counter = Counter@44ba70c

scala> c.subscribe(s)

scala> c.inc
got event: updated count to: 2

ObservableSet 做了类似的事情，它在使用 += 或 +- 方法添加或删除元素时调用发布方法，请参见以下示例(类 S 定义如上):

scala> class MySet extends HashSet[Int] with ObservableSet[Int] {       
     override def +=(elem: Int): this.type = super.+=(elem);
     override def -=(elem: Int): this.type = super.-=(elem);
     override def clear: Unit = super.clear;      
}

defined class MySet

scala> val set = new MySet
set: MySet = Set()

scala> val subS = new S[Any, Any]
subCol: S[Any,Any] = S@3e898802

scala> set.subscribe(subS)

scala> set += 1
got event: Include(NoLo,1)
res: set.type = Set(1)

我通过使用 Any 类型定义 S 来变得懒惰，但我无法立即正确输入，并且没有花太长时间试图弄清楚。