从Scala中选择trait继承常用方法

Question

假设我创建了一个混合在两个特征中的类,这两个特征都实现了一个通用方法,例如:

abstract class Base {
    var x:Int
    def adder:Int
}

trait One extends Base {
    def adder() = {x+=2; x}
}

trait Two extends Base {
    def adder() = {x+=3; x}
}

class WhichOne(var x:Int = 10) extends Base with One with Two

println((new WhichOne()).adder())

在运行时,Scala当然抱怨,因为它不知道更喜欢哪个特性:

$ scala MixUpTraitImplems.scala 
MixUpTraitImplems.scala:18: error: class WhichOne inherits conflicting members:
  method adder in trait One of type ()Int  and
  method adder in trait Two of type ()Int
(Note: this can be resolved by declaring an override in class WhichOne.)
class WhichOne(val x:Int = 10) extends Base with One with Two
      ^

当然,重写adder()意味着我继续执行新版本adder,但如果我不想要那个呢？如果我想使用addertrait 中显式包含的实现One或者Two怎么办？

Answer 1

您可以将其指定为修饰符super:override def adder() = super[One].adder().另请注意,这是编译时错误,而不是运行时!