你如何在Scala中返回迭代器？ [英] How do you return an Iterator in Scala?

问题描述

为了能够从方法/类中返回迭代器，我该怎么办？如何将该特征添加到类中？

What must I do in order to be able to return an Iterator from a method/class ? How would one add that trait to a class?

推荐答案

您可以扩展迭代器，这将要求你实现 next 和 hasNext 方法：

You can extend Iterator, which will require that you implement the next and hasNext methods:

  class MyAnswer extends Iterator[Int] {
    def hasNext = true
    def next = 42
  }

但是，如果你扩展 Iterable ，你将获得更大的灵活性，这需要你实现元素（或2.8中的 iterator ）：

But, you will get more flexibility if you extend Iterable, which requires you implement elements (or iterator in 2.8):

  class MyAnswer extends Iterable[Int] {
    def iterator = new Iterator[Int] {
      def hasNext = true
      def next = 42
    }
  }

一个常见的习惯用法似乎是将迭代器暴露给某些人私人收藏，像这样：

A common idiom seems to be to expose an iterator to some private collection, like this:

  class MyStooges extends Iterable[String] {
    private val stooges = List("Moe", "Larry", "Curly")
    def iterator = stooges.iterator
  }

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