拦截/装饰PartialFunction

Question

如何拦截PartialFunction？例如，在参与者中，如果我想在将以下接收方法传递到process方法之前打印出所有的内容：

class MyActor extends Actor {
  def receive : Receive = process
  def process : Receive = {
    case Some(x) => /* do one thing */ ()
    case None => /* do another thing */ ()
    case _ => /* do something else */ ()
  }
}

Answer 1

PartialFunction是一个您可以实现的特性。您不必使用case语法。

不幸的是，它没有一个方便的方法，以你所描述的方式作曲。最接近的是andThen方法，但是您传递的参数必须是一个常规函数，当实际的接收函数中没有处理参数时，这可能会导致匹配错误。所以你不得不用很长的路来写。

class MessageInterceptor(receiver: Receive) extends Receive {
  def apply(msg: Any) = {
    /* do whatever things here */
    receiver.apply(msg)
  }
  def isDefinedAt(msg: Any) = receiver.isDefinedAt(msg)
}

val process = new MessageInterceptor(receive)

Answer 2

def process: Receive = printMessage andThen {
  case Some(x) => /* do one thing */ ()
  case None => /* do another thing */ ()
  case _ => /* do something else */ ()
}

def printMessage: PartialFunction[Any, Any] = {
  case m => 
    println(m)
    m
}

Answer 3

我认为andThen方法是一个正确的选择：

def printEverything: PartialFunction[Any, Any] = {
case x =>
    println(x)
    x
}

并使用它：

def receive : Receive = printEverything andThen process