I've been developing in Android Studio and Xcode for a while... Also Ive been recently developing rails apps. After looking and finishing some tutorials on how to extend my rails app to a native mobile app I have just one doubt.
I'm sure that I understand what an API is, but I'm not sure if the fact of extending a rails app to a native mobile app will need it. Because I can create and respond to JSON without an API in the "original" controller.
What is the differences between creating an API and responding to the JSON in the "original" controller? Give a use case for both of them please.
By responding with JSON in your "normal" controller you will be building an API, you don't need the API-only version of rails, or any particular gem to build and API, just an agreed interface (request/responses) for your apps to get all the information you want.