CODEWITHSUNDEEP
objective-cioscore-data
Sharlon M. Balbalosa
Sharlon M. Balbalosa

Reputation: 1309

Sorting specific sections in Core Data

I am using NSFetchedResultsController to populate the tableView of my application it is group by section(in which case a category property in my core data object) I want to reorder the section manually not by alphabet order.

below is the code of what I have done so far

- (NSFetchedResultsController *)fetchedResultsController {

if (_fetchedResultsController != nil) {
    return _fetchedResultsController;
}

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription 
                               entityForName:@"Media" inManagedObjectContext:_context];
[fetchRequest setEntity:entity];

NSSortDescriptor *sort = [[NSSortDescriptor alloc] 
                          initWithKey:@"category" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];

[fetchRequest setFetchBatchSize:20];

NSFetchedResultsController *theFetchedResultsController = 
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
                                    managedObjectContext:_context sectionNameKeyPath:@"category" 
                                               cacheName:@"Root"];
self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;

return _fetchedResultsController;    

}

Thanks in advance!

Upvotes: 2

Views: 709

Answers (2)

Nicolas Bachschmidt
Nicolas Bachschmidt

Reputation: 6505

You can add a new entity named MediaCategory with:

  • an attribute name
  • an attribute rank
  • a to-many relationship media to the entity Media

and replace the category attribute with a relationship to MediaCategory.

Then, you can sort the request's result with the following sorts descriptors:

fetchRequest.sortDescriptors =
[NSArray arrayWithObjects:
 [[NSSortDescriptor alloc] initWithKey:@"category.rank" ascending:NO],
 [[NSSortDescriptor alloc] initWithKey:@"category.name" ascending:NO], // required only if many categories have the same rank
 nil];

and provide @"category.name" as the result controller's sectionNameKeyPath.

Upvotes: 2

lexa
lexa

Reputation: 424

If the task is to provide the custom order of sections, than you can subclass NSFetchedResultsController and implement

- (NSInteger)sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)sectionIndex;

and, if needed

@property (nonatomic, readonly) NSArray *sectionIndexTitles;
- (NSString *)sectionIndexTitleForSectionName:(NSString *)sectionName;

Upvotes: 2

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