turing complete with a stack of 0xdeadbeef
Welcome to the next post in my series about ReactiveCollectionsKit. Today I want to discuss diffing. Understanding diffing requires understanding two core concepts: identity and equality. These are two ideas that are also relevant and applicable to programming in general, and can often be confusing for newcomers.
I recently released a new open source project called ReactiveCollectionsKit. It is a modern, fast, and flexible library for building data-driven, declarative, reactive, and diffable collections and lists for iOS. This library is the culmination of everything I learned from building and maintaining IGListKit, ReactiveLists, and JSQDataSourcesKit. The 4th time’s a charm! 😅 🍀 I truly hope this is the last UICollectionView library I ever write and maintain. I think it will be. You can find the documentation here.
I was recently working on a project that uses modern collection views on iOS — that is, using diffable data sources, snapshots, and cell providers. I hooked up all the components and my collection view was working, or so I thought. I started to notice some very odd, unpredictable behavior when the collection view was updated. Some of the time, the cells were updated correctly. Other times, I would see duplicates and missing data. Here’s what went wrong.
This year at WWDC, some significant improvements and changes were announced for UICollectionView and UITableView. You can watch 10252: Make blazing fast lists and collection views for all the details, but I want to highlight some of them here.