Convert the for loop to accept ID type - objective-c

Question

I want to be able to reuse this method so it's not restricted by the class being called in the for loop declaration.
The problem is the compiler has no idea what id actually is, so I cannot use . notation on it. I need to cast it to a whatever type of event class i'll be passing it, instead of having to repeat the method for SpecialEvent1 SpecialEvent2 SpecialEvent3
So instead of for (SpecialEvent1 *event in day) I want to be able to do something like for (id event in day) but problem occurs when I try to access the time or duration property
- (NSArray *)sumDay:(NSArray *)day {
NSInteger morning = 0, afternoon = 0, evening = 0, night = 0;
for (SpecialEvent1 *event in day) {
NSDate *date = [NSDate dateWithTimeIntervalSinceReferenceDate:event.time];
NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitHour fromDate:date];
NSInteger hour = [components hour];
if (hour < 12) {
morning += event.duration;
}
else if (hour < 18) {
afternoon += event.duration;
}
else if (hour < 20) {
evening += event.duration;
}
else {
night += event.duration;
}
}
NSArray *sums = #[#(morning), #(afternoon), #(evening), #(night)];
return sums;
}

Answer 1

Assuming that you aren't interested in objects that don't have a time or duration property, you could define a protocol which says this:
#protocol TimedEvent <NSObject>
-(NSTimeInterval)time;
-(NSTimeInterval)duration;
#end
Then go through the array like this:
- (NSArray *)sumDay:(NSArray *)day {
NSInteger morning = 0, afternoon = 0, evening = 0, night = 0;
for (id<TimedEvent> event in day) {
if (![event conformsToProtocol:#protocol(TimedEvent)]) {
continue;
}
NSDate *date = [NSDate dateWithTimeIntervalSinceReferenceDate:event.time];
NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitHour fromDate:date];
NSInteger hour = [components hour];
if (hour < 12) {
morning += event.duration;
}
else if (hour < 18) {
afternoon += event.duration;
}
else if (hour < 20) {
evening += event.duration;
}
else {
night += event.duration;
}
}
NSArray *sums = #[#(morning), #(afternoon), #(evening), #(night)];
return sums;
}