Question

我正在做一个扩展类的简单scala应用程序。我收到一个错误，我不理解，即错误是位于类的“私人[this] val xc：Int”。

请在下面找到代码。

class Point(xc:Int ,yc:Int) {
    var x:Int =xc;
var y:Int =yc;

def move(dx:Int ,dy:Int)
{
    x=x+dx;
    y=y+dy;
    println("Point x location for Point Class = "+x)
    println("Point y location for Point Class = "+y)  
}
}

class Location(override val xc: Int, override val yc: Int,
   val zc :Int) extends Point(xc, yc){
   var z: Int = zc

   def move(dx: Int, dy: Int, dz: Int) {
      x = x + dx
      y = y + dy
      z = z + dz
      println ("Point x location : " + x);
      println ("Point y location : " + y);
      println ("Point z location : " + z);
   }
}
object Runner
{
    def main(arg : Array[String])
    {
//val pt = new Point(4,5);
//pt.move(4, 5)

val lo = new Location(1,2,3);
lo.move(1, 2,3)
    }
}

Answer 1

可能是因为在scala中覆盖私有/受保护成员的问题

https://issues.scala-lang.org/browse/SI-1994

你可以通过这种方式声明类Point来解决这个问题：

class Point(val xc:Int , val yc:Int)

*当你不在param中写val时，他们是私人成员

Answer 2

这有效：

class Point(var x: Int, var y: Int) {
  def move(dx: Int, dy: Int) = {
    x=x+dx
    y=y+dy
  }
}

class Location(
  x: Int,
  y: Int,
  var z :Int) extends Point(x, y) {

  def move(dx: Int, dy: Int, dz: Int) = {
    super.move(dx, dy)
    z = z + dz
  }
}

object Runner {
  def main(arg : Array[String]) = {
    val pt = new Point(4,5)
    pt.move(4, 5)

    val lo = new Location(1,2,3)
    lo.move(1, 2,3)
  }
}

问题扩展类 - 覆盖私有成员

2 个答案: