Rails service objects vs lib classes

Question

Short version: when should I put something into app/services instead of into lib/.

I've been going down the service objects route recently, but I realised that sometimes I can't really decide weather I should extract something into a service object (which I have in app/services) or into a class in my lib folder.

One thing I usually look for is if the class needs access to params or other controller-specific things (i.e. as a param in the initializer), then I tend to put it into services.

What is the convention here? Proof (links) would be nice :)

Answer 1

This is how I tend to think about code that goes in lib/:

• It is not coupled to my app's domain models.
• It can be reused on other projects.
• It can potentially become its own gem. Thus, putting it in lib/ is the first step in that direction.

Services:

• They tend to know a decent amount about the inner workings of domain models.
• Perform work that is specific to business domain in my app.
• Tend to be coupled to specific models.

Answer 2

IMO, services are an abstraction of your domain. Lib stuff is for convenience classes, other stuff that doesnt directly relate to your models.