类似unix的管道的ruby简单实现代码简单说明

此代码来自此处

class PipelineElement   attr_accessor :source   def initialize      @fiber_delegate = Fiber.new do         process      end   end   def |(other)      other.source = self      other   end   def resume      @fiber_delegate.resume   end   def process      while value = input         handle_value(value)      end   end   def handle_value(value)      output(value)   end   def input      @source.resume   end   def output(value)      Fiber.yield(value)   endendclass Producer < PipelineElement   def process     while true       value=readline.chomp       handle_value(value)     end   endendclass Filter < PipelineElement  def initialize    @line=1    super()  end  def handle_value(value)    value=sprintf("%5d %s",@line,value)    output(value)    @line=@line.succ  endendclass Consumer < PipelineElement  def handle_value(value)    puts value  endendproducer=Producer.newfilter=Filter.newconsumer=Consumer.newpipeline = producer | filter | consumerpipeline.resume

打印pipeline对象得到如下输出：

#<Consumer:0x8f08bf4 @fiber_delegate=#<Fiber:0x8f08a88>, @source=#<Filter:0x8f08db4 @line=1, @fiber_delegate=#<Fiber:0x8f08d60>, @source=#<Producer:0x8f09054 @fiber_delegate=#<Fiber:0x8f09038>>>>

PipelineElement段代码非常巧妙，将Fiber和Ruby的功能完全展示了出来。

producer=Producer.newfilter=Filter.newconsumer=Consumer.new

此段将纤程挂起，再使用

pipeline = producer | filter | consumer

依次调用|重载函数，最终返回consumer对象，其中|函数将把实例赋给other（即：|后的参数）的source属性

使用

pipeline.resume

运行consumer纤程，consumer执行process函数

  def process      while value = input         handle_value(value)      end   end

接下来调用父类的input函数跳到filter纤程，于是开始执行filter纤程的process，进而唤醒producer执行process，输入value并且handle_value，从而将value传回filter纤程的value，filter纤程接手handle_value

 def handle_value(value)    value=sprintf("%5d %s",@line,value)    output(value)    @line=@line.succ  end

再通过output将处理好的value传回consumer并且转回consumer纤程，consumer继续handle_value

  def handle_value(value)    puts value  end

此时输出value，同时开始下一次while循环，同时也开始了下一次连续的纤程循环。

另外从打印出来的pipeline可以很清楚的看到此过滤链的层次：

#<Consumer:0x8f08bf4 @fiber_delegate=#<Fiber:0x8f08a88>, @source=#<Filter:0x8f08db4 @line=1, @fiber_delegate=#<Fiber:0x8f08d60>, @source=#<Producer:0x8f09054 @fiber_delegate=#<Fiber:0x8f09038>>>>