nssortdescriptor

I can't wrap my head around how to do arbitrary sorting with a NSSortDescriptor. I want to do something like this: NSArray *sortAlgorithm = [NSArray arrayWithObjects:@"@", @"#", @"!", @"&", @"r", @"a", nil]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES comparator: ^(id obj1, id obj2) { NSComparisonResult comparisonResult; //Some code that uses sortAlgorithm. return comparisonResult; } ]; This would sort the objects by the key name so that any key that starts with @ , e.g. @home , would come before any key that starts with r , e.g. radical , and

I hava a core data application. And I want to fetch one kind of object, User . User have the property userId . I have another array with userId s, [1, 4, 3, 5] . And I would like to create a NSSortDescriptor that sorts my User objects based on the order of the userId s in the array. Is that possible, and how should I do that? Update I have now tried the following. I added a transformable property to my User object, where I store the user ids array. I have tried the following sort descriptor: sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"userId" ascending:YES comparator:

Ok, I initially wanted to make NSSortDescriptor of a request for NSFetchedResultsController to sort based on the property in my NSManagedObject subclass, but It obviously won't do it, because NSFetchedResultsController is limited to predicates and sort descriptors that work on the fetched entity and its relations, so I decided to create a transient attribute in my data model, synthesis the property for this attribute to ivar in my NSManagedObject subclass, and sort based on it. When running it, i got while executing fetch 'NSInvalidArgumentException', reason: 'keypath isActive not found in

I have an array of type "Restaurant" which has an NSSet of "Rating." Rating has an ID and a value. I want to sort the array of Restaurant's by rating with an ID of 01, from high to low. Something like the following, but how do I use the predicate and sort descriptor together on originalArray? NSPredicate *predicate = [NSPredicate predicateWithFormat:@"Rating.rating_id=%d", ratingID]; NSSortDescriptor *descriptor = [NSSortDescriptor sortDescriptorWithKey:@"currentValue" ascending:YES]; NSArray *sorted = [[originalArray allObjects] sortedArrayUsingDescriptors:[NSArray arrayWithObject:descriptor]