如何实现基本的枚举器类？

发布于 2024-12-09 19:47:32 字数 426 浏览 1 评论 0原文

我试图了解枚举器类的工作原理。具体来说，我不知道yielder对象是如何创建并传递给构造函数所采用的代码块的。

这是我的第一次尝试：

class MyEnumerator
  def initialize(&block)
    @block = block
  end 
  def next()
    @block.call self
  end 
  def yield(*args)
    args
  end 
end


num_gen = MyEnumerator.new do |yielder|
  (1..10).each { |num| yielder.yield num }
end

5.times { p num_gen.next }

它不起作用，当然是因为我不知道如何推进枚举器。有人可以帮助我了解如何实施它吗？

原文

I am trying to understand how Enumerator class works. Specifically, I do not know how the yielder object is created and passed to the code block that the constructor takes.

Here is my first try:

class MyEnumerator
  def initialize(&block)
    @block = block
  end 
  def next()
    @block.call self
  end 
  def yield(*args)
    args
  end 
end


num_gen = MyEnumerator.new do |yielder|
  (1..10).each { |num| yielder.yield num }
end

5.times { p num_gen.next }

It is not working, of course because I do not know how to advance the enumerator. Could somebody help me in understanding how I can implement it?

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心病无药医 2024-12-16 19:47:33

这是构建基本枚举器的一种方法（根据托克兰的建议更新）：

class MyEnumerator
  def initialize
    @fiber = Fiber.new { yield Fiber }
  end

  def next
    @fiber.resume
  end
end

用法：

>> num_gen = MyEnumerator.new { |f| (1..10).each { |x| f.yield x } }
=> #<MyEnumerator:0x007fd6ab8f4b28 @fiber=#<Fiber:0x007fd6ab8f4ab0>>
>> num_gen.next
=> 1
>> num_gen.next
=> 2
>> num_gen.next
=> 3
>> num_gen.next
=> 4

Here's one way to build a basic enumerator (updated with tokland's suggestion):

class MyEnumerator
  def initialize
    @fiber = Fiber.new { yield Fiber }
  end

  def next
    @fiber.resume
  end
end

Usage:

>> num_gen = MyEnumerator.new { |f| (1..10).each { |x| f.yield x } }
=> #<MyEnumerator:0x007fd6ab8f4b28 @fiber=#<Fiber:0x007fd6ab8f4ab0>>
>> num_gen.next
=> 1
>> num_gen.next
=> 2
>> num_gen.next
=> 3
>> num_gen.next
=> 4

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