Terminating app due to uncaught exception ‘NSUnknownKeyException‘, reason: ‘[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key your_property_name.
You can face NSUnknownKey Exception during your I Phone development. This exception occurs if you created an outlet connection for any controll. I named it your_property_name.
@property (weak, nonatomic) IBOutlet UIButton *your_property_name;
So if you rename your property or delete that outlet then you can face this exception. Because you have deleted that property but compiler still looking that outlet.