Question

I have the following class in my mind:

abstract class MyClass (data: MyData) {

  def update(): MyClass = {
    new MyClass(process())
  }

  def process(): MyData = {
    ...
  }

}

然而,抽象的班级不能上调,因为“新日志”(工艺)

Answer 1

怎样做这样的事情? <代码>MyClass与具体类型不符。当然,所有具体班级都必须采用一种实际返回新的<代码>的方法。 Self 。

trait MyClass[+Self <: MyClass[Self]] {
  def update(): Self = {
    makeNew(process())
  }

  def process(): MyData = {
    // ...
  }

  protected def makeNew(data: MyData): Self
}

class Concrete0 extends MyClass[Concrete0] {
  protected def makeNew(data: MyData) = new Concrete0
}

class RefinedConcrete0 extends Concrete0 with MyClass[RefinedConcrete0] {
  override protected def makeNew(data: MyData) = new RefinedConcrete0
}

信贷:IttayD's second Update to his 问题。

Answer 2

To completly avoid implementing almost identical method in all subclasses you would need to use reflection. I guess that would be your last resort if you have chosen Scala. So here is how to minimize the repetitive code:

// additional parameter: a factory function
abstract class MyClass(data: MyData, makeNew: MyData => MyClass) {

  def update(): MyClass = {
    makeNew(process())
  }
  def process(): MyData = {
    ...
  }
}

class Concrete(data: MyData) extends MyClass(data, new Concrete(_))

这样,你就只能重复最短的碎块,用于对子级进行即时处理。

友情链接