Scala多继承以及AOP

class Human{
  println("Human")
}

trait TTeacher extends Human { 
  println("TTeacher")
  def teach 
} 

trait PianoPlayer extends Human { 
  println("PianoPlayer")
  def playPiano = {println("I am playing piano. ")} 
} 

class PianoTeacher extends Human with TTeacher with PianoPlayer { //构造PianoTeacher实例时，按照从左至右的顺序依次完成，仅构造一次
    override def teach = {println("I am training students. ")} 
}

object UseTrait extends App{
   val t1 = new PianoTeacher
   t1.playPiano 
   t1.teach 
}

结果：
Human
TTeacher
PianoPlayer
I am playing piano.
I am training students.

//AOP
trait Action { 
    def doAction 
}

trait TBeforeAfter extends Action { 
    abstract override def doAction { 
        println("Initialization") 
        super.doAction //因为调用了父类的抽象方法，所以本方法也是抽象的。super.doAction最终会在子类Work中实现，有点类似于模板方法设计模式。
        println("Destroyed") 
    } 
}

class Work extends Action{
     override def doAction = println("Working...")
}

object UseTrait extends App{
    val work = new Work with TBeforeAfter
    work.doAction
}

结果：
Initialization
Working...
Destroyed