Sorting array of custom objects using the value of an internal object's instance variable

Question

(sorry about the long title)

I have a custom object Person, which in turn has an NSSet which has several custom objects called Appointment. A Person therefo

Answer 1

You can use sort descriptors and KVC collection operators:

NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"appointments.@min.startSecond" ascending:YES];

For example, in a CoreData fetch:

NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Person"];

NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"appointments.@min.startSecond" ascending:YES];
[request setSortDescriptors:@[sortDescriptor]];

NSError *error = nil;
NSArray *sortedResults = [context executeFetchRequest:request error:&error];

Or just sorting an array:

NSArray *people = @[...];
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"appointments.@min.startSecond" ascending:YES];

NSArray *sortedPeople = [people sortedArrayUsingDescriptors:@[sortDescriptor]];

More information on KVC collection operators can be found in the KVC Programming Guide.