I’ve been researching this for a while and I think there are a number of solutions, but I’m not sure they are that good. It may be that I’ve missed something 🙂
I have two tables. For each record in TableA there are multiple records in TableB. I.e. a one to many relationship. I’ve mapped it out in core data and generated the classes. So far so good.
My table view based UI needs to look like this:
Section 1
Cell 1: Table A: field1
Cell 2: Table A: field2
-----
Section 2
Cell 1: Table B: record 1: field1
Cell 2: Table B: record 2: field1
....
When I’m in my tableView:cellForRowAtIndexPath: it’s easy to handle section 1 cells because they are different fields from the single Table A record. The section 2 cells are different. Each time tableView:cellForRowAtIndexPath: is called I need to get the correct Table B record from Table A’s NSSet. And thats the problem.
NSSet doco indicates that it does not garrantee the order. Which means that if I want a specific record based on an index I have several possible techniques:
- Add a sort descriptor to the core data query and use the fast enumeration to get to the record I want. I don’t know if this will work because we are still working with an NSSet.
- Sort the NSSet using a sort descriptor after getting the data to generate a NSArray and store that in a property before starting the table load.
- I’m now thinking of a third option which is to write a decorator for an NSSet which acts like a NSArray and allows me to specify a sort field and automatically tracks changes to the NSSet. Tricky but might pay off in the long run.
neither of these answers seem that great. Is there a better way to do this?
I’ve ended up with a NSArray being stored in the controller and sorting the NSSet records into it.