How to sort Core Data fetched properties

Question

The Core Data Documentation states that:

The fetch request associated with the [fetched] property can have a sort ordering, and thus the fetched prope

Answer 1

Jeff, if the strings are right-aligned, you could just sort on the strings; " 123" > " 23" and so on. But iirc ascii space is after the numbers, and if so, then what you would do is create a dynamic property that is an NSNumber (which supports the compare: method), and use the numberFromString: method to make a number from the string. Then you can specify the number field in the sort. In the interface:

@property NSString *stringIsaNumber; // in the data model
@property NSNumber *number;

in the implementation:

@dynamic stringIsaNumber; 
- (NSNumber *) number ;
{ return [self.stringIsaNumber numberFromString]; }
- (void) setNumber:(NSNumber *)value;
{ self.stringIsaNumber = [NSString stringWithFormat:@"%5i",value) }

ps plz forgive coding errors, this is off the top of my head.

Answer 2

Using Tim Shadel's great answer I added per-NSManagedObject subclass sorting...

...in Tier.m (which is a NSManagedObject subclass)...

+ (void)initialize
{
    if(self == [Tier class])
    {
        NSFetchedPropertyDescription *displayLessonPropertyDescription = [[[Tier entityDescription] propertiesByName] objectForKey:@"displayLesson"];
        NSFetchRequest *fetchRequest = [displayLessonPropertyDescription fetchRequest];

        NSSortDescriptor *sortByName = [[NSSortDescriptor alloc] initWithKey:@"displayOrder" ascending:YES];
       [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortByName]];
        [sortByName release];
    }
}