Most of the apps interact with server, So there must be network layer abstraction to interact with server.
NetworkLayerProtocolUrlSessesion demonstrate a way of abstraction and interaction with server. It uses protocol oriented programming to communicate and also uses same for Unit Test. It helps in
1 Flexibility, To be able to edit or add new urls efficiently.
2 Readability, Makes your code more readable.
3 Code safety, with typed parameters. This allow all the pre-compilation goodness we expect from Xcode.
4 Easy debugging, meaning being able to insert logs before and after web requests.
5 Testable Network Code.
ApiManager.swift class is single source of communication between your app and server. It uses Alamofire to send GET/POST request.This always return JSON data.
UserApiManager.swift class is abstraction layer between URLSession and your app logic code. This always return your data model.
NetworkLayerSessionTests includes Unit test of network layer
MockApiManager.swift uses a protocol oriented way to stub the request with local data.