ActionController filter initialization

[pmeinhardt]

Hi, I encountered this strange behaviour, when trying to set up a controller *_filter from an incuded module:

The module code looks similar to this (shortened it for readability)

module Tracking

  module ControllerAdditions
    def track(selectors = [])
      selectors.each do |sel|
        before_filter sel do |con|
          puts "#{sel}d #{con.class} #{con}"
        end
        before_filter sel, nil # rails bug? dummy
      end
    end
  end

  def self.included(base)
    base.extend ControllerAdditions
  end

end

It is then included in a controller as follows:

class SomeController < ApplicationController
  include Tracking

  track [:foo]

  def foo
    redirect_to "http://example.org"
  end
end

Problem is, that

• if I use after_filter instead of before_filter and leave out the dummy filter, the controller will throw a "multiple redirects" error
• if I use before_filter without the dummy, nothing gets logged at all

I use Rails 3.1.3.

Thanks for your help.

Regards,
Paul

[arunagw]

Hey @pmeinhardt have you got any solution for this?? Or this problem still exists for you?

[pmeinhardt]

Hey, I haven't had the time to dig into it since then. However, if you have any clue on how to solve this, I'd appreciate any hints.

It's strange I have to call the before_filter method twice.

Another solution that I considered in the meantime was using cuts to hook into arbitrary methods outside the regular Rails initialize, create, update and destroy hooks. There's a performance penalty to it (method execution is about ~13 times slower than with explicit "tracking" calls), but it allows me to prevent scattering the tracking methods all over the place.

This (instrumenting methods) should be a common problem in web applications/analytics so if anyone can point me to sth. better, I'd be more than grateful.

[carlosantoniodasilva]

Hey @pmeinhardt, I think I may not be understanding quite right what you're trying to achieve here.

By giving a symbol to before_filter, you're telling this filter to run a method, not to run on a specific action. By giving a block, you're asking to run that block by passing the controller instance to it.

So, if I got your idea right, it'd look something like this:

module Tracking
  module ControllerAdditions
    def track(*actions)
      before_filter only: actions do |con|
        puts "Tracking [#{con.action_name}]: #{con.class} #{con}"
      end
    end
  end

  def self.included(base)
    base.extend ControllerAdditions
  end
end

# controller
class PostsController < ApplicationController
  include Tracking
  track :index

  def index
    @posts = Post.all
  end
end

# logger output
# Tracking [index]: PostsController #<PostsController:0x007fa064161ac8>

This was tested with a newly generated app and Rails 3.2.3. If that's not the path you're trying to go here, please try to explain a little bit better so we can verify it that's a real issue. Thanks.

ps: about your question related to instrumentation, the best thing for it nowadays I believe would be AS::Notifications.

[pmeinhardt]

Argh. Yes @carlosantoniodasilva, you're absolutely right. I completely used the before_filter method in a wrong way here. What I was really trying to achieve was "before :action do ...". It seems totally obvious now, thanks to you. When I threw this together, I should've given it another look. Thanks :)

Thanks also for the hint about AS::Notifications, I'll dig right into it.

Cheers,
Paul

[carlosantoniodasilva]

Ok, great, thanks :). AS::Notifications it totally worth a try. Cheers.