Running before filter in plugin. Is there any other way?

Question

I am writing my first plugin, and in that plugin, I need to run a method for some controller/action pairs. For this plugin the configuration yml looks like this -

track1:
   start_action: "home", "index"
   end_action: "user", "create"

So, in my plugin I will first read above yml file. After that I want to run an action say - first_function as before_filter to home-controller index-action and I would be running second_function as after_filter for user-controller create-action.

But I couldn't figure out how can I write filters for this, which will be declared in plugin and will run for actions specified by user in above yml files.

Please help !

Answer 1

I see two options to reach your goal.

First approach: declare both the filters inside the ApplicationController and inside the filter check whether the controller_name and action_name match any in your yaml-configuration. If they match, execute it, if not ignore.

In code that would like

class ApplicationController

  before_filter :start_action_with_check
  after_filter :end_action_with_check

  def start_action_with_check
    c_name, a_name = CONFIG['track1']['start_action'].split(', ')
    if c_name == controller_name && a_name == action_name 
      do_start_action
    end
  end

  ...

I hope you get the idea.

Second approach: a clean way to define before_filter is to define them in a module. Normally you would use the self.included method to define the before_filter, but of course, you can define them conditionally. For example:

class HomeController < ApplicationController

  include StartOrEndAction

  ...
end

and in lib/start_or_end_action.rb you write

module StartOrEndAction

  def self.included(base)
    # e.g. for the start-action        
    c_name, a_name CONFIG['track1']['start_action'].split(', ')
    if c_name == controller_name && a_name == action_name 
      base.before_filter :do_start_action
    end
    # and do the same for the after_filter
  end

  def do_start_action
    ...
  end

  def do_end_action
    ...
  end
end 

The advantage of the second solution is that the before_filter and after_filter are only defined when needed. The disadvantage is that you will have to include the module into each controller where you could possible configure the before-filter to take place. The first has the advantage that any controller is covered, and you get a little overhead checking the before- and after filter.

Hope this helps.