Apple's system frameworks make a lot of functionality available to us developers, from auto layout to calendrical calculations, locales, and formatting. Although the internal workings of these classes are not available to us, some implementation details are actually open source: auto layout is built on the Cassowary project, while NSCalendar, NSLocale, and the NSFormatter subclasses are built on top of the icucore framework. But because these projects are open-source, there's nothing stopping us from seeing how they work under the hood. However, Apple does keep some goodies to themselves (persistent Touch Bar items) and some system functionalities are only available through opaque mechanisms (AirDrop through UIActivityController). In this talk I detail how to search for hidden functionality, the wonders of disassembly and decompilation, and how to follow the code trails through to the methods you want.
Recorded and produced live by Stefan Völker.