You might want to clarify your question: > do you really have no access to SDK code as a reference? You get headers but no source. While Darwin is in theory o

You might want to clarify your question: > do you really have no access to SDK code as a reference? You get headers but no source. While Darwin is in theory open source, UIKit, et. al. are not. > I got to that assembly code part and just sat there and re-read it again and again. If you're referring to the screenshot, Xcode dumps you into disassembly in cases where the stack is not in your code. 0 -[MoTextView endFloatingCursor] is the author's code. The remainder is UIKit. Also, most of the line items are _prefixed which indicates a private method upon whose existence (much less implementation) is not reliable. As the author mentions, the stack on the left is usually enough to diagnose problems. It's also one more thing that makes me fight using Swift; all of the name-mangling and opaque to the Objective C runtime additions make this problem even harder.