scala隐式类:继承参数的所有成员

Question

我有一个非常有用的隐式类,我想扩展GenIterable:

  import scala.collection.GenIterable
  implicit class WhatUpTho[S<:GenIterable[T],T](s:S) extends GenIterable[T]{
    def whatUpTho = println("sup yo")
  }

不幸的是,编译器不会让我写这个,因为它缺少79所需的方法或属性trait GenIterable.我想将所有WhatUpTho未明确定义的请求推迟到其s参数.

我该如何做到这一点？

Answer 1

没有必要扩展GenIterable [T].

object Conversions {
  implicit class WhatUpTho[S <: GenIterable[_]](s:S) {
    def whatUpTho = println("sup yo")
  }
}

import Conversions._

val s = List(1, 2, 3)
s.whatUpTho

关于泛型:

// Depending on the signature of your functions, you may
// have to split them into multiple classes.
object Conversions {

  implicit class TypeOfCollectionMatters[S <: GenIterable[_]](s:S) {
    def func1(): S = ...
    def func2(t: S) = ...
  }

  implicit class TypeOfElementsMatters[T](s: GenIterable[T]) {
    def func3(): T = ...
    def func4(t: T) = ...
  }

   // If you need both, implicit conversions will not work.
  class BothMatters[S <: GenIterable[T], T](s: S) {
    def func5: (T, S) = ...
  }
}

import Conversions._

val s = List(1, 2, 3)
s.func1
s.func2(List(4,5,6))
s.func3
s.func4(7)

// You have to do it youself.
new BothMatters[List[Int], Int](s).func5