Xcode 8 Breakpoint in file not working
I had the same problem with an old project. Select Product(located at top menu bar) -> Scheme -> EditScheme and I solved this issue by clicking on "Debug Executable", as shown in Picture. Maybe this will help someone else too.
In my case breakpoint was not hit in just one callback, so I changed "Swift Compiler" "Optimization Level" to "No optimization" in project target build settings for debug, and it started working in Xcode 9.3 as well as AppCode.
Below patch is work for me. From the menu bar, select Product -> Scheme -> Edit Scheme -> Select Profile -> Set Build Configuration to BUILD. Please review below-attached screenshot.
