How do I call multiple procs?

Question

I could use some help on this one, given this code:

result1, result2, result3 = do_stuff {
  method_1
  method_2
  method_3
}

I would like to be able to write a method called do_stuff that can call each line of that block individually and return a result for each line/block. Can it be done? Am I going about this the wrong way? Something like this (doesn't work at all) is what I am thinking.

def do_stuff(&block)
  block.each_block do |block|
    block.call
  end
end

EDIT: What I am trying to accomplish is to be able to run each method/block call inside the method "do_stuff" in parallel (in it's own thread) and also add some logging around each method call.

Maybe you could tell us what you're really trying to accomplish. — mu is too short, Aug 15 '11 at 04:33
I want to be able to run each method/block call inside the method "do_stuff" in parallel (in it's own thread) and also add some logging around each method call. — efleming, Aug 15 '11 at 12:19

score 1 · Answer 1 · answered Aug 15 '11 at 06:04

I agree with mu above, you should explain what you are trying to do, as there is probably a more suitable pattern to use.

BTW, you can do what you ask for with a minor change:

result1, result2 = do_stuff {
  [
    method_1,
    method_2,
    method_3
  ]
}

or, perhaps, more elegantly, without the block:

result1, result2 = [
  method_1,
  method_2,
  method_3
]

:)

score 1 · Answer 2 · answered Aug 16 '11 at 07:45

OK, it looks clearer after the question was updated. You could do something like this, using method_missing, instance_eval and threads:

class Parallelizer
  class << self
    def run(receiver, &block)
      @receiver = receiver
      instance_eval &block
      # wait for all threads to finish
      @threads.each{|t| t.join}
      @results
    end

    def method_missing *args, &block
      @threads ||= []
      @results ||= []
      @threads.push Thread.new{
        # you could add here custom wrappings
        @results.push(@receiver.send(*args, &block))
      }
    end
  end
end

class Test
  def take_a_break name, sec
    puts "#{name} taking a break for #{sec} seconds"
    Kernel.sleep sec
    puts "#{name} done."
    name
  end
end

t = Test.new

results = Parallelizer.run(t) do
  take_a_break 'foo', 3
  take_a_break 'bar', 2
  take_a_break 'baz', 1
end

Be careful, though, that this is not well-tested and I am not sure how threadsafe.

How do I call multiple procs?

2 Answers2