Some sorting problems (Core Data beginner)

Question

Hi all.

Maybe there is a simple solution to this, but I'm getting headache of this, I'm fairly new with all this Core Data stuff:

I have a BankAccount class/entity with an "index" attribute, used for sorting, and a "transactions" to-many relationship to the Transaction class/entity. This Transaction entity has a "date" attribute, that I want to use for sorting too.

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity:[NSEntityDescription entityForName:@"BankAccount" inManagedObjectContext:self.managedObjectContext]];
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"index" ascending:YES];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];

This works well and delivers me the BankAccount objects nicely sorted by "index". But, each BankAccount object contains a NSSet "transactions" that is, ofcourse, not sorted at all. How can I get these transactions sorted by the "date" attribute, and is this possible within the same fetch request?

Many thanks in advance.

Answer 1

To do this you would need to fetch the Transactions ordered.

What you would need is:

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity:[NSEntityDescription entityForName:@"Transaction"
                                    inManagedObjectContext:self.managedObjectContext]]; 
[fetchRequest setPropertiesToFetch :[NSArray arrayWithObjects:@"date", @"bankAccount", nil]];
[fetchRequest setSortDescriptors:[NSArray arrayWithObjects:
                                  [[[NSSortDescriptor alloc] initWithKey:@"date"
                                                               ascending:YES
                                                                selector:@selector(compare:)] autorelease],
                                  [[[NSSortDescriptor alloc] initWithKey:@"bankAccount.index"
                                                               ascending:YES] autorelease],
                                  nil]];

I'm assuming that Transaction is the name of the entity for transactions, and that bankAccount is the relationship from entity Transaction to BankAccount.