Why am I getting the superclass and not the subclass in my method call? - objective-c

Question

I have this class, which is a port from a C# abstract class; this is the .h file:
#interface Schedule : NSObject {
}
#property (strong, nonatomic) NSDate *apptStartTime;
#property (strong, nonatomic) NSDate *apptEndTime;
#property (strong, nonatomic) NSString *key;
-(BOOL) occursOnDate: (NSDate *) timeOfAppointment;
#end
This is the .m file for Schedule:
#implementation Schedule {
}
#synthesize apptStartTime;
#synthesize apptEndTime;
#synthesize key;
/**
The OccursOnDate method is abstract and must be implemented by subclasses. When passed a date, the schedulers must determine if an appointment falls on that date. If one does, the method should return true. If not, the method returns false.
*/
-(BOOL) occursOnDate: (NSDate *) dateOfAppointment {
return YES:
}
Because it's a C# abstract class, it has to be overridden (or subclassed) which I have done here (this is the .h file):
#interface SingleSchedule : Schedule {
}
#property (strong,nonatomic) NSDate *apptDate;
-(BOOL) occursOnDate: (NSDate *)date;
#end
This is the .m file:
#implementation SingleSchedule {
}
#synthesize apptDate;
-(BOOL) occursOnDate: (NSDate *)date {
return (apptDate == date); // <--------- TODO where is apptDate set?
}
This is where I call the occursOnDate class, expecting to get the subcclass, but I get the superclass class instead:
-(void) addAppointmentsForDate:(NSDate *)checkDate scheduleSet: (NSMutableSet *)setOfSchedules appointmentSet:(NSMutableSet *)setOfAppts {
Schedule *sc = [[Schedule alloc]init];
Appointment *newAppt = [[Appointment alloc]init];
NSArray *scheduleArray = [setOfSchedules allObjects];
for(int i = 0; i < scheduleArray.count; i++) {
if([sc occursOnDate: checkDate]) { // <-------- method called is the superclass, not the override
newAppt = [self generateAppointment:checkDate andSchedule: scheduleArray [i]];
[setOfAppts addObject:newAppt];
}
}
}
What am I missing here to be able to get the subclass method and not the other? (I have looked at SO and Google but found nothing which would answer this question exactly).

Answer 1

The base class implementation is being called because sc is of type Schedule, not SingleSchedule. When you instantiate a class, the new object is aware of it's own implementation and it's base class chain, but the object is not aware of it's inherited classes.
Maybe what you want is:
SingleSchedule *sc = [[SingleSchedule alloc]init];