From Idea To Reality: Designing An App With Sketch And Xcode
Everyone has an idea for a mobile app, from your mom to the guy you met in line at the grocery store. You might even be one of those people, if you are reading this tutorial. Building your own app really gives you the ability to create anything you can imagine. For some people, the idea is the easy part; when it comes to making it a reality, they have no clue where to start.
Source: Smashing Magazine