Copy Story Board connection problem: ' Nsunknownkeyexception ', Reason: ' [<viewcontroller 0x7ff3da732de0> Setvalue:forundefinedkey:]: This class is not ... '

' Nsunknownkeyexception ', Reason: ' [<viewcontroller 0x7ff3da732de0> Setvalue:forundefinedkey:]: This class was not Key value coding-compliant for the key Headimageview. '

The reason for this is that the storyboard is a copy of the other items, copied over, the connection is also copied at the same time, in general, because a control in the previous project has been connected to a variable in the Viewcontroller, then the variable was deleted, but the connection is not deleted, Causes the corresponding key to be found at startup and throws the above exception.

Workaround:

Locate the controller, right-click on the properties associated with a control, delete all lines from the previous item (note where there is a yellow warning), recompile and run

Remove and rerun to resolve

Copy Story Board connection problem: ' Nsunknownkeyexception ', Reason: ' [<viewcontroller 0x7ff3da732de0> Setvalue:forundefinedkey:]: This class is not ... '