Xcode Version 9.0.1
Error occurs whenever control-drag to connect ui and source from storyboard to .swift file like the screenshot.
Terminating app due to uncaught exception ‘NSUnknownKeyException’, reason: ‘[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key
Try control-drag from an UI image in storyboard to a source code like the above image.
And then build and run an application.
After this, the both ways works.
1st – control-drag from a title of an UI in storyboard to a source file.
2nd – control-drag from an UI image in story board to a source file.
I don’t understand why. But it works for me.