Question

I have been using Rails for over 4 years so obviously I like Rails and like doing things the Rails Way and sometimes I unknowingly fall to the dark side.

I recently picked up Clean Code by Uncle Bob. I am on Chapter 6 and a bit confused whether we as rails developers break the very fundamental rule of OO design, i.e. Law of Demeter or encapsulation? The Law of Demeter states that an object should not know the innards of another object and it should not invoke methods on objects that are returned by a method because when you do that then it suggests one object knows too much about the other object.

But very often we call methods on another object from a model. For example, when we have a relationship like ‘An order belongs to a user’. Then very often we end up doing order.user.name or to prevent it from looking like a train wreck we set up a delegate to do order.name.

1. Isn’t that still like breaking the Law of Demeter or encapsulation ?

2. The other question is: is ActiveRecord just a Data Structure or Data Transfer Object that interfaces with the database?

3. If yes, then don’t we create a Hybrid Structure, i.e. half object and half data structure by putting our business rules in ActiveRecord Models?

Answer 1

Rails is Rails. What else is there to say. Yes, some of the idioms in Rails violate good design principles. But we tolerate this because it’s the Rails way.

Having said that, there is far too much model usage in most rails applications. Far too often I see view code directly accessing models. I see business rules folded into the active record object. A better approach would be to isolate the business rules from the active records and isolate the views from the models. This wouldn’t violate any rails idioms, and would make rails applications a lot more flexible and maintainable.