Code Brawl Entry: Methods taking multiple blocks

README.md

Simple Instance Callback Hash

This is an entry to Code Brawl: Methods taking multiple blocks

The basic idea here is to have your callbacks setup through a method call and not sent as an argument to the method. You can then have these callbacks adapt depending on the other parameters sent through the method. After the method had been executed, it is deleted from the hash.

Example Usage:

class Test
  def setup_callbacks
    callback.hello do |string|
      puts string
    end
  end

  def request
    setup_callbacks
    callback.hello('Hello World')
  end
end
Test.new.request

cbhash.rb

require 'delegate'

class CallbackHash < DelegateClass(Hash)
  def initialize
    super(Hash.new)
  end

  def method_missing(
        method_name, *arguments, &block)
    if self[method_name].nil?
      self[method_name] = block
    else
      self[method_name].call(*arguments)
      self.delete(method_name)
    end
  end
end

module Kernel
  def callback
    @cb ||= CallbackHash.new
  end
end

Why delete the method?

This is a fine approach, but it's more per object than per method.

I think this example misses the point, as it doesn't allow you to provide a method with multiple blocks.

@JEG2
yep it is per object mostly making the callback available to the whole object to execute* -- That's why the name ;)

@rogerbraun
Because you might have other methods using the same key to call a block
(since if the key exists, it would simply return the block and not assign a new one)
but it would be best to have it different to avoid executing the wrong code*

@jeremyevans
hmmm, it actually depends, I wanted to try not passing anything at all and I was coming from the idea that the end goal was simply to be able to call your callbacks in your method. Which in turn is the reason for passing multiple blocks to the method -- which I tried to eliminate. ;)