Xcode 8.3.3 may have bug that prevents solution from running

There may be a bad bug in Xcode 8.3.3 that is happening when compiling the exercise in Chapter 19 (Pg345 finishes it).
I was unable to get the program to run although there were no errors.
I compared my code to that of the solution, which did run, and rearranged all my code to flow in the same order as the solution code was given.
It still did not run. Then I started changing the exact syntax of statements to match the solution code.
I was lucky, the first statement I changed was the long statement (in my code) that in the solution in the book was shortened by using two lines.
When it compiled, everything worked perfectly. Go figure!
Anyway, here is the difference between working and not working.

Chapter 19 UIGestureRecognizer and UIMenuController

func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith
OtherGestureRecognizer: UIGestureRecognizer) -> Bool {
return true

Doesn’t work

func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer,shouldRecognizeSimultaneouslyWithOtherGestureRecognizer: UIGestureRecognizer) -> Bool {
return true

Did you make sure that they had the correct and same signature?

Compare UIGestureRecognizerDelegate

The missed white space caused the problem because it separates the external argument name from the internal one:

  • shouldRecognizeSimultaneouslyWith - external;
  • otherGestureRecognizer - internal.

If you connect them together you corrupt the signature of the method.