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Comment by johnthealy3 | Hacker News Reader

I was feeling okay about this article until seeing this colossal punt:

> That said, the real intention behind this pattern is to keep the API/view/controller lightweight and free of excessive logic, which is something we would strongly advocate. Having logic inside model methods is a lesser evil, but you may want to consider keeping models lightweight and focused on the data layer. To make this work, you will need to figure out a new pattern and put your business logic in some layer that is in between the data layer and the API/presentational layer.

Having fat models is definitely a problem I'm having, and it's nice to see it's a problem for the author too, but the advice "figure it out" is presented without any explicit suggestions.

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Procedural/functional code. Splitting your models up more by features than high level things (e.g. having a separate CustomerBilling rather than putting it in Customer). Component based architectures. Service layer to coordinate models. Etc. Also, this is/was a common problem (at least, the god class aspect) in games that the industry has slowly solved over the past 20 years, so that's another place you can look for inspiration.

Further, unless you know you're going to scale in the beginning, I would recommend refactoring/evolving over time. It doesn't do anyone any favors by having 10 models to represent your Customer if your Customer is already relatively thin.

My team has run into the same problem in a large Rails app. We decided on a combination of service objects and data access objects (DAO) where appropriate. In a lot of cases this has really helped with the grep-ability of our codebase.

Service objects allow us to encapsulate complex operations that touch several domains and tables through a simple API. They're just plain objects.

DAOs fulfill a specific case of providing a simple CRUD API to a domain. We use a lot of DynamoDB so the DAO allows us to hide the complexity of reaching out to several tables in order to return a result. We also make sure that the DAO returns an immutable object that can't reach back into the datastore like an ActiveRecord object can (#save! methods come to mind).

The difference between a service object and a DAO is a little blurry but is enforced through quick design discussion and code reviews.

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