ios - How can I test if an attribute of a CoreData object is null? -

ios - How can I test if an attribute of a CoreData object is null? -

i want test if nsnumber attribute of nsmanageobject subclass has been set or not. note, attribute of nsnumber / integer16 have tried several approaches none worked (these below evaluate false):

// note: patient.zyklus_laenge of nsnumber (integer16) // not work id value = patient.zyklus_laenge; if (value == [nsnull null]) { self.zykluslaengetextfield.text = [nsstring stringwithformat:@"%d", 28]; } else { self.zykluslaengetextfield.text = [nsstring stringwithformat:@"%@", patient.zyklus_laenge]; } // not work if (!patient.zyklus_laenge) { self.zykluslaengetextfield.text = [nsstring stringwithformat:@"%d", 28]; } else { self.zykluslaengetextfield.text = [nsstring stringwithformat:@"%@", patient.zyklus_laenge]; } // not work if ([patient.zyklus_laenge isequal:nil]) { self.zykluslaengetextfield.text = [nsstring stringwithformat:@"%d", 28]; } else { self.zykluslaengetextfield.text = [nsstring stringwithformat:@"%@", patient.zyklus_laenge]; } // not work if (patient.zyklus_laenge == nil) { self.zykluslaengetextfield.text = [nsstring stringwithformat:@"%d", 28]; } else { self.zykluslaengetextfield.text = [nsstring stringwithformat:@"%@", patient.zyklus_laenge]; }

can enlighten me , explain me why these not working?

the solution set attribute in core info required default value , test code:

if (!patient.zyklus_laenge) { self.zykluslaengetextfield.text = [nsstring stringwithformat:@"%d", 28]; } else { self.zykluslaengetextfield.text = [nsstring stringwithformat:@"%@", patient.zyklus_laenge]; }

ios objective-c core-data nsmanagedobject