如何确保函数接收与当前对象相同的参数类型? [英] How do I make sure a function receives the same parameter type as the current object?

问题描述

abstract class A {
  protected[this] type ThisType = this.type
  protected[this] type OtherType = this.type 

  def assign(other: OtherType): ThisType
}

class B extends A {
  def assign(other: OtherType): ThisType = ???
}

class C extends A {
  def assign(other: OtherType): ThisType = ???
}

class D extends C {
  def assign(other: OtherType): ThisType = ???
}

如何确保在assign的B对象中收到的另一个类型也是B的对象.例如我该如何有效地写一些东西:

How do I make sure the other type received in assign of and object of type B is also B. e.g. how can I write something effectively like:

def f1(p1: A, p2: A) = p1.assign(p2)
def f2[T <: A](p1: T, p2: T) = p1.assign(p2)

我遇到以下错误:

注意:实际上ThisType和OtherType应该相同，但是我将它们分开了，所以我可以尝试不同的选择.

NB: Actually ThisType and OtherType should be the same but I seperated them so I can try out different options.

推荐答案

使用另一种方法可以使用 F绑定多态性:

abstract class A[T <: A[T]] {
  def assign(other: T): T
}

class C extends A[C] {
  override def assign(other: C): T = ???
}

def f1[T <: A[T]](p1: T, p2: T) = p1.assign(p2)

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