Active record organisation for maintainability and testability

Question

Hello friends!

Some of my AR classes are starting to... bulge around the waist. I'm starting to think it might be time to put them on a diet. Probably the biggest concern I have is that there's just so much code in one file, I'm considering breaking out validations, associations and groups of related methods into modules. Are there any other alternatives I haven't considered?

I'd also like to do the same thing with my tests (I'm using shoulda with test/spec if that makes a different)...

Your thoughts would be greatly appreciated.

Answer 1

It's quite normal to extract everything, or, most-common behaviour with associations into plugins with class methods like "acts_as_fat_model".

In general one of rails mvc idioms is "Fat models - skinny controllers". It's a good sign that your models (and not controllers) are fat.

Answer 2

I'm familiar with your problem. Some models in my projects were also getting too big to work pleasantly with them. I found a small piece of code (I think on PaulBarry.com) which enables you to split your models into several files.

concerned_with makes it possible to place parts of your model in a subfolder. You put, for example, the following line in your original model:

class User < ActiveRecord::Base
    concerned_with :validation
end

Then you create a file in 'models/user/validation.rb' which contains your validations:

class User
    validates_presence_of :username
end

Just put this code into an initializers file in your Rails project and you can use this nice feature!

class << ActiveRecord::Base
  def concerned_with(*concerns)
    concerns.each do |concern|
      require_dependency "#{name.underscore}/#{concern}"
    end
  end
end