Providing an ActiveRecord-like before_filter capability to arbitrary Ruby classes

gistfile1.rb

# First the end result of what we want:

class Foo
  before_hook :whoa
  before_hook :amazing

  def test
    puts "This is kinda cool!"
  end

  def amazing
    puts "Pretty amazing!"
  end

  def whoa
    puts "Whoa!"
  end
end

Foo.new.test

# OUTPUT BELOW

Whoa!
Pretty amazing!
This is kinda cool!

# And this is how I implemented it:

# Demonstrates how to provide ActiveRecord-like before_filter
# hooks for arbitrary classes.

module ExecutionHooks
  # this method is invoked whenever a new instance method is added to a class
  def method_added(method_name)
    # do nothing if the method that was added was an actual hook method, or
    # if it already had hooks added to it
    return if hooks.include?(method_name) || hooked_methods.include?(method_name)
    add_hooks_to(method_name)
  end

  # this is the DSL method that classes use to add before hooks
  def before_hook(method_name)
    hooks << method_name
  end

  # keeps track of all before hooks
  def hooks
    @hooks ||= []
  end

  private

  # keeps track of all currently hooked methods
  def hooked_methods
    @hooked_methods ||= []
  end

  def add_hooks_to(method_name)
    # add this method to known hook mappings to avoid infinite
    # recursion when we redefine the method below
    hooked_methods << method_name

    # grab the original method definition
    original_method = instance_method(method_name)

    # re-define the method, but notice how we reference the original
    # method definition
    define_method(method_name) do |*args, &block|
      # invoke the hook methods
      self.class.hooks.each do |hook|
        method(hook).call
      end

      # now invoke the original method
      original_method.bind(self).call(*args, &block)
    end
  end
end

# Make it available to all classes.
Class.send(:include, ExecutionHooks)

What I was looking for. Right on. Thanks!

It doesn't work here with ruby 2

undefined method before_hook for Foo:Class (NoMethodError)

It works with ruby 2, maybe you missed the last line to include in all classes

Class.send(:include, ExecutionHooks)

Or for a single class just

extend ExecutionHooks

In the class file

Thanks for this. I created different solution with this

http://stackoverflow.com/questions/29785454/call-before-methods-in-model-on-ruby/29837450#29837450

Thanks for this!
Any suggestions on passing a variable to the before_hook?

e.g.: before_hook :refresh_user_token(user)

Thanks a lot, it helps me track of execution order of methods call. Just modified line 72 to method(hook).call(method_name) and set before_hook : print_executed_action

Thanks.. very inspiring

I have created a version for a simple around_action like functionality:

• https://gist.github.com/fguillen/bac172d48b73148ca911c0fed2a03953

Thanks for this solution.
Any idea on how can we extend this before_hook for Superclass as well? This before_hook works when hook is added to a method of any class and method is called directly but doesn't work when the hook is added to a method of its superclass.
Thanks in advance!