ruby on Rails dto objects - Where do you store them?

Question

Does anyone here use DTO's to transfer data from the controller to the view? If so, where would you recommend storing those files? /apps/dtos, and then let them mirror the views dir structure? Any recommendations on testing these animals with rspec?

Answer 1

Please don't listen to the other answers. They are terrible. Rails helpers are terrible. Using rails models everywhere is terrible. I am begging you, design your application properly and decide if you need DTOs or not. Decide if you actually want to have rails models to handle things other than communication with the database. Decide if you actually want to not have a layer between your app and rails and so on and so forth. Rails design is suitable for only small apps or apps that have to be developed super quickly. But if it's not something trivial and you expect to develop it for some time, please invest your time into proper design. Don't be afraid to break Rails conveniences. And may the force with you.

Answer 2

The Rails convention is not to use distributed tiers for controller and view layers. The separation is there, but it is logical and relatively thin/lightweight compared to the types of frameworks you see in Java land.

The basic architecture is that the controller sets instance variables that are available in the corresponding view. In the general case, the instance variables will be model instances or collections of model instances (coming from the database). Models should be the core of your business logic. Controllers coordinate flows of data. Views display it. Helpers are used to format display values in the view ... anything that takes a model value and does something just for display purposes (you may find that a helper method used repeatedly may actually be better off on the model itself).

However, if you find that a view needs knowledge of many different models, you might find it easier to wrap models into another object at a higher-level of abstraction. Nothing prevents you from creating non-active-record objects that collect and coordinate your actual AR models. You can then instantiate these objects in the controller, and have them available to the view. You generally have to be at a pretty dense level of complexity in the controller to need this type of thing.

I would tend to throw such objects into apps/models - Rails already loads everything in this directory, keeps things easy from a config/expectation point of view.

Answer 3

If you're coming from a .NET or J2EE background you may be thinking about patterns like DTO. You may or may not be surprised (and possibly happy) to learn that Rails doesn't do things that way by convention.

In particular there is no need at all to formally transfer (or store) serialized objects between the controllers and views. Instance variables (typically model attribute values) created in the controller are available within the view for free as provided by the framework without any additional programming effort needed.