Steven Troughton-Smith points to an article by Brad Larson:
I always find it more effective to learn new programming concepts by building projects using them, so I decided to do the same for Apple’s new Swift language. I also wanted to see how well it would interact with my open source GPUImage framework. As a result, I made GPUImage fully Swift-compatible and I’ve built and committed to the GitHub repository a couple of Swift sample applications. I wanted to write down some of the things that I learned when building these.
It’s interesting to see programmers get their hands dirty with what most likely will be the way forward for iOS developers.