Form Objects vs. Inheritance

gistfile1.rb

# The purpose of this gist is to propose use of inheritance when upgrading objects to have "more functionality".

# For example:

#  Lets say you have a `company` model and your project manager purposes a huge pivot to your existing application.  
#  Now new fields are "required" for the new companies you create.  Unfortunately adding validators to the existing 
#  `company` model will cause things to blow up.  You could create a form object for the new forms with form specific 
#  validators.  Several issues are now introduced:
  
#  1) There can be several form objects for the company.  Each with a slight difference in logic.
#  2) Any time you change something with the company model, every form object needs to be looked at.

# Instead you can simply create a new object that inherits from Company... 

class FirmCompany < Company
  
end

#  Now the new validators can be added to the `FirmCompany` object.  The goal would be to move all the validators to the 
#  original `Company` object once the old data is cleaned up.  In the mean time the application will not blow up while 
#  the old data is being sanitized.

+1

+1

yep

Have you considered the other way pivot, when you need to disable a validation rule?

also, why is #1 an issue? squashing different behaviors into one class increases the complexity of code, so it's always better to have a few small robust classes than one huge 500-line and 100-method monster.

One more use case: validating nested associations

    class Company
      has_one :address
      validates_nested_attributes_for :address
    end
    class Address
    end

Let's say there is a form where you need to add validates :foo to Address not breaking legacy code where this field is not required.
Subclassing both Company and Address for this purpose would be too much, right?

Actually, a lot of people in Rails community are using form objects, so maybe it is not that bad?

http://railscasts.com/episodes/416-form-objects
https://medium.com/p/84b6849c886e
http://nicksda.apotomo.de/2013/05/reform-decouple-your-forms-from-your-models/
http://robots.thoughtbot.com/activemodel-form-objects
http://rhnh.net/2012/12/03/form-objects-in-rails

And a few thoughts about inheritance in general: http://stackoverflow.com/questions/49002/prefer-composition-over-inheritance

i definitely agree there is a time and place for form objects. i think the problem here was it made the code more complex by repeating validations and logic for simple CRUD actions that had no side effects (unlike something akin to user registration which may trigger notifications, etc.)