Today I decided to write about a list of rules that I follow when working with Rails. This rules are by no mean the way to go for everyone take what you think is correct and try to use it. I will try to update this list as new rules appears on my experiment.


  • Do not call any query methods directly to a model (Finders methods are ok to call).
  • Do not catch active record exceptions.
  • Do not use if statements inside actions (Use service or interactor objects for handling the business logic).
  • Do not use filters.
  • Return just one instance variable from your actions.


  • Just test for the proper http code if developing an API

Active Record

  • Reference models within other models for anything else expose a public method.
  • Wrap methods for create/update/save to define a persistence API for the application.
  • Wrap in scopes every query methods for the model.
  • Do not throw exceptions from methods return true or false.
  • Do not use callbacks be explicit about your methods calls.
  • Extend behavior of models using decorators.
  • Validations are a good thing to use inside models if they turn out to be too complex use a validator object.


  • Just test behavior avoid testing implementation things like
    expect(model).to has_one(another_model)

    are discourage.

  • Same thing for validations; test it indirectly through testing behavior.


  • Do not use helpers for formatting data use presenters objects.
  • Do not use predicate helper methods in your views for handling conditionals use view models.
  • Wrap validations for forms within Form Objects.


  • Do not test views; there’s no logic in there


Probably you will be asking where should I put all the business logic for my application; well you have a plethora of concepts from the object oriented design world. You can use interactors or services, decorators, adapters, presenters, value objects; try to find what’s right for your case and implement it. Remember that Rails is just a framework it is not your application.