rails-devise-pundit | Rails 5.0 starter app | Authentication library

Service objects are for things that don't fit well in the normal MVC paradigm. They're typically for business logic that would otherwise make your models or controllers too fat. Typically they have no state (that's held in a model) and do things like speak to APIs or other business logic. Service objects let you keep your models thin and focused, and each service object is also thin and focused on doing one thing.

Rails Service Objects: A Comprehensive Guide has examples of using service objects to manage talking to Twitter, or encapsulating complex database transactions which might cross multiple models.

Service Objects in Ruby on Rails…and you shows creating a service object to manage the new user registration process.

The EngineYard blog posted Using Services to Keep Your Rails Controllers Clean and DRY with an example of a service object which does credit card processing.

If you're looking for the origins, Service objects in Rails will help you design clean and maintainable code. Here's how. is from 2014 when they were coming on the scene.

Services has the benefit of concentrating the core logic of the application in a separate object, instead of scattering it around controllers and models.

The common characteristic among all services is their lifecycle:

• accept input
• perform work
• return result

If this sounds an awful lot like what a function does, you're right! They even go so far as to recommend using call as the public method name on the service, just like a Proc. You can think of service objects as a way to name and organize what would otherwise be a big subroutine.

Anatomy of a Rails Service Object addresses the difference between a service object and a concern. It covers the advantages a service object has over modules. It goes into some detail about what makes a good service object including...

• Do not store state
• Use instance methods, not class methods
• There should be very few public methods
• Method parameters should be value objects, either to be operated on or needed as input
• Methods should return rich result objects and not booleans
• Dependent service objects should be accessible via private methods, and created either in the constructor or lazily

For example, if you have an application which subscribes users to lists that might be three models: User, List, Subscription.