Swift 5.9 brought powerful observation tools to the language, but unfortunately they only work in iOS 17, macOS 14, tvOS 17, watchOS 10, and newer. But by some accounts, less than 50% of devices are on iOS 17, and so most developers will not be able to make use of these tools for a few more years. So we have backported the observation tools to work on Apple’s platforms going all the way back to iOS 13, macOS 10.15, tvOS 13, watchOS 6, and we’ve released it as an open-source library. This means y...