issue with sorting data in UITableview

I have implement a UItable with data sourced via Core Data. The table works fine and presents the data correctly, drills down.. etc.

However, it has the following problem: it presen开发者_StackOverflowts the content data in a different order every time. I would like it at least to appear consistently or even better alphabetically.

Any ideas on why this might be happening or a specific property or method I should be reviewing in the docuemntation?

Help much appreciated

You need to set an NSSortDescriptor on your NSFetchRequest

NSSortDescriptor *sortDescriptorName = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES selector:@selector(caseInsensitiveCompare:)];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptorName]];

Then create your NSFetchedResultsController with the fetchRequest object.

This would cause your list to appear sorted alphabetically using the property "name" and ignore case while sorting.

You can simply add a sort descriptor to the request. In this example, the data object has a numeric column for "sortOrder", but you could sort on most anything.

- (NSMutableArray *)loadData {
NSManagedObjectContext *context = [self managedObjectContext];

NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"NameOfEntity" inManagedObjectContext:context];
[request setEntity:entity];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"sortOrder" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
[sortDescriptors release];
[sortDescriptor release];

NSError *error = nil;

NSMutableArray *mutableFetchResults = [[context executeFetchRequest:request error:&error] mutableCopy];
if (mutableFetchResults == nil) {
    // Handle the error.
}

[request release];

return [mutableFetchResults autorelease];
}

I have not done much with CoreData other than to read about it and review some examples, but I would say this:

It sounds like your data is simply coming out of CoreData unsorted, and the order is in fact not guaranteed UNLESS you provide some additional hint about how you would like it sorted, with say a sort descriptor or something.

Sorry I can't provide a concrete reference, but there has to be a way to both fetch data and specify the order in which it is returned.

Alternatively, you could (behind the scenes) fetch all the table data from CoreData and then sort it yourself, but I think that defeats the purpose of using CoreData in the first place and discards a lot of the functionality of CoreData that is likely more efficient than anything you could write yourself to massage the data.