Dwifft!
Dwifft is a small Swift library
... useful, and the other thing is a very concretely useful thing based off the first thing. It can help you build a substantially better user experience if you have table/collection views with dynamic content in your app. There is some non-trivial index math inside of this diff algorithm that is easy to screw up. Dwifft has 100% test coverage on all of its core algorithms.