如何使用 sub class 的实例访问 super class 的成员

Question

我正在练习 JavaTpoint 中的这段代码，以学习 Scala 中的继承。但是我无法从值初始化为零的 class Vehicle 访问成员 Bike。我尝试了超类型引用，但它仍然显示覆盖值。你能告诉我如何使用 Bike class 的实例访问值 speed = 0 吗？这是代码和输出。提前致谢。

   class Vehicle{  
  val speed = 0
  println("In vehicle constructor " +speed)
    def run(){  
        println(s"vehicle is running at $speed")  
    }  
}  

class Bike extends Vehicle{  
  override val speed = 100
     override def run(){  
     super.run()
        println(s"Bike is running at $speed km/hr")  
    }  
}  

object MainObject3{  
    def main(args:Array[String]){  
      var b = new Bike()  
        b.run()  
        var v = new Vehicle()
        v.run()
        var ve:Vehicle=new Bike()
      println("SuperType reference" + ve.speed) 
    ve.run()
    }  
}

Answer 1

我可以想到两个选项。

1) 在覆盖之前保存该值。

class Bike extends Vehicle{
  val oldspeed = speed
  override val speed = 100
  override def run(){
    println(s"Vehicle started at $oldspeed km/hr")
    println(s"Bike is running at $speed km/hr")
  }
}

2) 在基数class中使值成为def。然后就可以在子class.

中访问了

class Vehicle{
  def speed = 0
  def run(): Unit = {...}
}

class Bike extends Vehicle{
  override val speed = 100
  override def run(){
    println(s"Vehicle started at ${super.speed} km/hr")
    println(s"Bike is running at $speed km/hr")
  }
}

如何使用 sub class 的实例访问 super class 的成员

How to access members of super class using an instance of the sub class

inheritance

scala

member

instance