This content was released on Nov 5 2019. The official support period is 6-months from this date.
Download and install Hopper, find the right UIKit binary in Xcode and start disassembling the binary.
This is a companion discussion topic for the original entry at https://www.kodeco.com/5443810-exploring-uikit-internals-with-hopper-disassembler/lessons/2