hooks

gistfile1.txt

#borrow from https://github.com/apotonick/hooks
#changes:
#remove block call support
#extend ActiveSupport::Concern into module to support nested module dependency
#add ability to pass multiple call_back methods params to a trigger
#for example: after_failed :job1, :job2..

require 'active_support/concern'

module Hooks
  module InheritableAttribute
    # Creates an inheritable attribute with accessors in the singleton class. Derived classes inherit the
    # attributes. This is especially helpful with arrays or hashes that are extended in the inheritance
    # chain. Note that you have to initialize the inheritable attribute.
    #
    # Example:
    #
    #   class Cat
    #     inheritable_attr :drinks
    #     self.drinks = ["Becks"]
    #
    #   class Garfield < Cat
    #     self.drinks << "Fireman's 4"
    #
    # and then, later
    #
    #   Cat.drinks      #=> ["Becks"]
    #   Garfield.drinks #=> ["Becks", "Fireman's 4"]
    def inheritable_attr(name)
      instance_eval %Q{
        def #{name}=(v)
          @#{name} = v
        end
        def #{name}
          return @#{name} unless superclass.respond_to?(:#{name}) and value = superclass.#{name}
          @#{name} ||= value.clone # only do this once.
        end
      }
    end
  end
end

module Hooks

  extend ActiveSupport::Concern

  def self.included(base)
    base.extend InheritableAttribute
    base.extend ClassMethods
  end

  module ClassMethods
    def define_hook(name)
      accessor_name = "_#{name}_callbacks"
      setup_hook_accessors(accessor_name)
      define_hook_writer(name, accessor_name)
    end

    def run_hook(name, *args)
      run_hook_for(name, self, *args)
    end

    def run_hook_for(name, scope, *args)
      callbacks_for_hook(name).each do |callback|
        scope.send(callback, *args)
      end
    end

    def callbacks_for_hook(name)
      send("_#{name}_callbacks")
    end

    private

    #get all the call_back methods name 
    #for example, after_falied :job1, :job2
    #so it will create instance _after_failed_call_backs = [:job1, :job2]
    def define_hook_writer(hook, accessor_name)
      instance_eval %Q{
        def #{hook}(*methods)
          methods.each do |m|
            #{accessor_name} << m
          end
        end
      }
    end

    def setup_hook_accessors(accessor_name)
      inheritable_attr(accessor_name)
      send("#{accessor_name}=", [])  # initialize ivar.
    end
  end

  def run_hook(name, *args)
    self.class.run_hook_for(name, self, *args)
  end
end