Extracting a Rails application into a plugin or engine

Question

I have a Rails 2.3 application which I would like to extract into a plugin, or engine. The application has user authentication, and basic cms capabilities supported by ancestry plugin.

I want to extract the logic for the application into a plugin/engine so that I can use this code for future projects, with a different "skin" or "theme" if required.

I'm not entirely sure I actually understand the difference between plugin and engine concepts, so that would be a good first point.

What is the best approach, are there any good starting points, links, explanations, examples that I should follow. Also, with the release of R3 to consider, is there anything that I should be aware of for that, with regards to plugins etc.

I am going to start off by watching Ryan's http://railscasts.com/episodes/149-rails-engines but obviously thats over a year old now, so one of the challenges I'm faced with is finding the most up to date and relevant information on this subject.

All tips and help gratefully received.

Answer 1

Writing a plugin is an entirely different process than writing an app, if you already have your app code it should be straightforward converting it into a plugin.

Consider that if you use third-party plugins in your app it could get pretty messy.

Answer 2

Actually, converting an application is pretty straigtforward. Just create a plugin-folder, put an app-folder inside containing all yor model-views-controllers folders, and that's it.

You will have to manage your migrations yourself though. Also you have to define rake-tasks to copy files to your public folder. I think the railscasts is still pretty up-to-date, if anything it is now easier in rails 2.3.

Good luck!