There are a lot of APIs out there, a lot of networking layers, a lot of abstractions, I’m going to offer just one way to start building Swift models backed by a RESTful API. Out of personal preference, PromiseKit will be used instead of callbacks and ObjectMapper will be used to convert between JSON and Swift objects.
On my most recent project I was building the client-side of a mobile app. I was a few days ahead of the backend in terms of functionality, but what was really giving me issue was the absence of any kind of test data. Rather than kill my momentum and allow the backend to block my development, I decided to build a quick API “emulator” that would allow the client to perform actions and feed it randomized test data.