AFNetworking,

The Model-View-Controller (MVC) design pattern is great for the longevity and maintainability of an iOS application’s codebase… but you may find yourself adding similar functions to multiple models as your app grows. In cases such as networking, moving common logic out of your model classes and into singleton helper classes can be a better approach. In this article, I’ll teach you how to set up a centralized singleton networking object that, decoupled from micro-level MVC components, can be reused throughout your application.