Question

我正在尝试在地图上创建订阅者。

这是代码：

type Msg = Message[(SomeObject)] with undoable
class mySub extends Subscriber[Msg,HashMap] {
  def notify(pub:HashMap, evt: Msg) = {
       evt match{
            case Include(NoLo,x) => println(x)
       }   
  }

}

在上面的通知中，如果我只是打印evt我得到输出： - 包括（NoLo，someobject）..但如果我尝试案例包括代码不会编译说找到：包括所需：消息

是否包含Message的子类？你如何测试不同的消息，如包括，删除等..

Answer 1

我可以编译：

import collection.mutable._
import collection.script._
type K = Int
type V = Int
type Msg = Message[(K, V)] with Undoable
class mySub extends Subscriber[Msg, HashMap[K, V]] {
  def notify(pub: HashMap[K, V], evt: Msg) = {
    (evt: Message[(K, V)]) match {
      case Include(NoLo, x) => println(x)
    }
  }
}

有趣的是，当Undoable混合在......时，模式匹配将无法编译。

Answer 2

稍微冗长一点，但这就是我想出的：

import scala.collection.mutable.{HashMap, Subscriber, Publisher, Undoable, ObservableMap}
import scala.collection.script.{Message, Update, Include, Reset, Remove, Script}

class MySub extends Subscriber[Message[(Int,Int)] with Undoable, ObservableMap[Int, Int]] {
def notify(pub: ObservableMap[Int, Int], evt: Message[(Int, Int)] with Undoable) = evt match {
   case update: Update[(Int, Int)] => println("Update: " + update )
   case include: Include[(Int, Int)] => println("Include: " + include )
   case reset: Reset[(Int, Int)] => println("Reset:" + reset)
   case remove: Remove[(Int, Int)] => println("Remove: " + remove)
   case script: Script[(Int, Int)] => println("Sript: " + script)
 }
}

如您所知，您必须在Message的子类上引用elem val来获取键或值。

scala.collection.script.Message上的scala模式匹配

2 个答案: