I'm trying to understand how some apps look so custom and beautiful, but most of the controls that are used in it look nothing like what comes with Xcode. What's the "secret"? Are app designers just putting one large background image in the app in Xcode, then lay transparent controls on top? I've heard a lot about Sketch, is this what it's used for?
I'm not a designer, but a coder for the web and I'm trying to make the transition to native app development. I just can't understand how all these mobile apps look vastly different when only a few controls are included in Xcode. So I just ask a designer to create a UI in Sketch, then make that he background image in my Xcode project? That's for any help or insight.
You can make your app look custom designed using native controllers. For example you can customise your navigation bar by replacing the View with a custom image. Or customise your TableViewController by creating some custom cells(adding image vies, changing the background view or cell's height). You can also you some open source frameworks like : TWTSideMenuViewController
But this comes with a cost because the developer may not support it's framework for future releases.