Here’s a nice tutorial showing how to create a slick transition between two buttons using Core Graphics in Swift from Robert Böhnke.
Robert explains how he drew the different buttons, used Paint Code for automatically creating code from images for the trickier paths, and explains step by step how he animated each individual line stroke to achieve a “hamburger button” type effect.
This image shows the final animation effect:
You can find the tutorial on Robert’s blog here.
The source code can be found on Github here.
A nice guide and a stunning effect.