Modularize application

Hello. What´s the best way to extend a rails base application?. I explain myself. I have been writting an e-commerce application and while in production extending it to client needings.

I have rewritten the code adding the new features and controlling all these changes with subversion.

Now I would wish to modularize the application starting with the simplest possible e-commerce application and having all the "extra" features isolated.

I have been taking a look at engines but I´m not sure if I need this level of complexity.

I also know generators but I don´t feel confortable with this approach.

What´s the best way to isolate a base application and keep growing it with new features?.

Needings are: *add,overwrite models,controllers,helpers methods *add,overwrite views with possibility to render the overwritten view from the new view.This is the most complex part because several modules could overwrite the same view. *for css,js and images I´m not sure if i would use generators or perhaps the posibility to define several public directories with preference order.

Any suggestions?. Thanks Excuse my poor english. Alfredo Garcia - Spain

It sounds like these are some ambitious goals! I'd recommend starting with the simplest components and extracting more and more as necessary to keep it manageable. For the simple functionality extracting it into Modules in /lib and including them in your Models and Controllers can help to keep things DRY and cohesive.

Example: class Commerce::CommerceController < ApplicationController   include CustomerLoader   layout 'commerce'   ... end

module CustomerLoader   # Makes cart and customer available as ActionView helper method.   def self.included(base)     base.send :helper_method, :current_customer, :cart if base.respond_to? :helper_method   end

  protected   def current_customer     ...   end

  def cart     ...   end end

After you get some Modules separated it may make sense to group those together and bundle it as a gem. I don't have much experience with that but it is an excellent tool for code sharing and reuse, especially with Rails 2.1 config.gem shizzy.

Additionally you can use inheritance to isolate the places that need to change. Be sure that you're dealing with is-a relationships though.

Example:   module Commerce     class ProductsController < CommerceController       ...     end   end

For your CSS and .js I think that having different layouts that include the correct files would be the best way. You could even choose the layout dynamically.

For some more tips look around the code of some of your favorite plugins and see how they've handled these issues. The ways I've suggested are just a few and won't get you all the way there, but I hope that they've been a good starting point and will open up the discussion to some more techniques.

Hope to have helped, Dimo