Swift - this class is not key value coding-compliant for the key txtbox."

error code : 

Thread 1: "[<HelloWord.ViewController 0x7fe880506c50> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key txtbox."

 

 

해결방법 :  커넥션 삭제 후 재연결 -> Reconnect after deleting connection