在Ruby中传递的块中引用调用对象 [英] Reference the invoking object in the passed block in Ruby

问题描述

是否有任何方法可以在被调用的块内保留被调用的对象.例如，这些块有什么方法可以访问方法batman或类SuperHeros

Is there any way to get hold of the invoked object inside the block thats being called. For instance, is there any way for the blocks to get access to the scope of the method batman or the class SuperHeros

class SuperHeros

  attr_accessor :news

  def initialize
    @news = []
  end

  def batman task
    puts "Batman: #{task} - done"
    yield "feed cat"
    @news << task
  end

end

cat_woman = lambda do |task| 
  puts "Cat Woman: #{task} - done" 
  # invoker.news << task
end

robin = lambda do |task| 
  puts "Robin: #{task} - done"
  # invoker.news << task
end


characters = SuperHeros.new
characters.batman("kick Joker's ass", &cat_woman)
characters.batman("break Bane's bones", &robin)

推荐答案

您可以使用类似于 Savon中使用宝石:

You can use something similar to Instance eval with delegation pattern, used - for example - in Savon gem:

def batman(task, &block)
  @original_self = eval('self', block.binding)
  puts "Batman: #{task} - done"
  instance_exec('feed cat', &block)
  @news << task
end

private

def method_missing(method, *args, &block)
  if @original_self
    @original_self.send(method, *args, &block)
  else
    super
  end
end

在这种方法中，当您在传递给batman方法的块中调用方法(使用隐式接收器)时，将在SuperHeros实例的上下文中调用该方法.如果没有可用的此类方法，则调用(通过method_missing)转到原始块self.

In this approach, when you call method (with implicit receiver) inside block passed into batman method, it's called in the context of SuperHeros instance. If there is no such method available, the call goes (through method_missing) to original block self.

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