I had the same problem, the design was already prepared in the Sketch and wanted to get the code from it easily. My friends and I've working on a solution for converting design into UI codes, last 2 years.
We've developed Monday Hero platform to improve the development phase and actually save time for repetitive code. https://www.mondayhero.io
In Monday Hero, you can upload design and get responsive code with Storyboard, Xib or only code options. You can also select the elements on the design, group them as you wish for your code library and download it easily in like 15 minutes :) It was a dream of me to get the UI code that easily, I hope it can be also useful to you.