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

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，我会得到输出：- Include(NoLo, someobject)..但是如果我尝试 case Include 代码将无法编译说找到： Include required: Message

Is Include not a subclass of信息？如何测试不同的消息，例如包含、删除等。

Answer 1

我可以编译这个：

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 混合在一起时，模式匹配将无法编译......

Answer 2

更详细一点，但这是我想到的：

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)
 }
}

正如您所注意到的，您必须引用 Message 子类上的 elem val 才能获取键或值。