Hierarchic MVC in Rails 3?

I've read about HMVC (Hierarchic Model View Controller) and it's flexible structure.

Have a look at this picture:

http://techportal.inviqa.com/wp-开发者_高级运维content/uploads/2010/02/MVC-HMVC.png

I wonder if the Rails 3 plugins are the answer to HMVC in Rails 3?

Based on the comments to Toby's answer it seems that you would like to be able to have MVC apps used as a component within a new app. Rails Engines (See http://rails-engines.org) provides this functionality. You simply install the engines gem and place apps in vendor/plugins and its modles/views/controller are all accessible.

This does not really conform to HMVC where the controllers in the new app delegate to other controllers. But like Toby I do not see the advantage of that.

What is nice about the Engines approach is that you can over ride any of models in the plugin by just adding a version of the model to the new apps app/model folder (same applies for views and controllers)

I have overidden app/views/layouts to give my Authentication app/plugin the same look and feel as the application it is included in.

For Rails 3 Railtie takes the place of engines and is officially supported (and actually used - Action Mailer is a Railtie plugin. I have not used it myself yet though.

Check it out at http://edgeapi.rubyonrails.org/classes/Rails/Railtie.html

A nice write up on it is also here http://www.igvita.com/2010/08/04/rails-3-internals-railtie-creating-plugins/

Rails has had plugins for a long time.

I doubt there is a technical reason why a controller couldn't dispatch to another controller, passing the request object along a chain. I just don't know what you gain by doing so - the diagram looks like spaghetti.

To me it's a misuse of MVC. I would suggest it is much simpler and more maintainable to push logic into lower-level models and classes and create a single controller that fronts the this logic, rather than creating a chain of controllers.

In the Rails 3 blog post, DHH mentioned the Cells project. I haven't used it but I am going to check it out.

The cart example shows well how that kind of functionality might clean up your application code. Code which retrieves data should be placed somewhere in controller. In every action or in a before filter. The Cell seems to be much better solution.

Please look at this rubyonrails-talk post: https://groups.google.com/forum/#!topic/rubyonrails-talk/0c4TT7UOGCw