Director.m

// some ObjectiveC class implementation
// manages some models within a CoreData ManagedObjectContext 

//
//  example for getting first object within a NSSet by object's "start" attribute 
//

-(Asset *)getFirstAssetByStart
{
    Asset *asset = nil;
    
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"start" ascending:YES];
    NSArray* sortDescriptors = [[NSArray alloc] initWithObjects: sortDescriptor, nil];
    NSArray *assetsOrderedByStart = [[_package.assets allObjects] sortedArrayUsingDescriptors:sortDescriptors];
    asset = [assetsOrderedByStart firstObject];

    return asset;
}