I remember when Core Image first launched on iOS and there were only about 15 filters that had been ported across from macOS. That's certainly not the case any more though and you may need some help figuring out which one you need. Enter Noah Gilmore with his new CIFilter documentation site. There's an app too, if you want to test them out.
Are Apple working on a declarative, Swift only UI API for us to use in the future? Maybe! But why wait for that when you could give this one from Tim Donnelly a go instead? It works alongside UIKit so you don't have to adopt it wholesale if you do decide to give it a try.
Do you do A/B testing in your app? If you do, has it started to spread havoc in your codebase? Arlind Aliu has some advice on how to cleanly add split testing of content, design and behaviour to your app.
I love apps that take state restoration seriously and make sure I end up back where I was no matter whether or not the app has been silently terminated in the background since I last used it. Keith Harrison gives us a way to use Sourcery to make the implementation of it a little easier.