DCI and Decoupling Business Logic from Ruby on Rails Part 1

I've been applying DCI with my team for the past few months and have found it allows for much greater flexibility in design. We can keep our classes small and cohesive and in turn we find the code easier to understand in a lot of ways. Specifically, the fact that design can be driven by scenarios centered around the contexts gives a clear flow of logic from the controller to the domain.

In a lot of ways DCI will almost seem a bit like having a meta-MVC within your MVC application. I like to think of it as a MVC-like pattern for the domain, decoupling your domain from the infrastructure of the web-tier.

If you are unfamiliar with DCI, I'd recommend checking out the Oredev videos where it was first introduced:

http://vimeo.com/8235574

http://vimeo.com/8235394

Also Jim Gray is currently working on a book (I've pre-ordered and get the chapters as they are being written) http://clean-ruby.com/

This is an interesting approach.

One change I would make is in the testing of the lib directory. I've found it best to separate the testing of the lib directory contents from the unit and functional tests that are baked into Rails. It requires a bit of custom setup, but it's easy to reuse in other applications.

1. Create a test/lib directory

2. Create a lib/tasks/test_libs.rake file

3. Put the following into the Rake file[1]:

    namespace :test do
      desc "Test libraries"
      Rake::TestTask.new(:libs) do |t|
        t.libs << "test"
        t.pattern = 'test/lib/**/*_test.rb'
        t.verbose = false
      end
    end

    lib_task = Rake::Task["test:libs"]
    test_task = Rake::Task[:test]
    test_task.enhance { lib_task.invoke }

4. Run `rake test:libs` to test just your lib directory.

[1] Credit goes to http://stackoverflow.com/a/1588496 for this Rake task.

Does anybody else see similarity between this

  authenticate = SApp::AuthenticateUser.authenticate(...
  action = authenticate.action
  if action != :login_error
    redirect_to "/#{action}"
  ...
  def find_account
    @account = SApp::FindAccount.find(@account_subdomain)
  end

and this http://en.wikipedia.org/wiki/Inner-platform_effect http://thedailywtf.com/Articles/Soft_Coding.aspx