Where should I release an object? Can it release itself? - iphone

Question

I want to get friends information from Facebook and save it with Core Data.
I build a FriendsManager Class that gets the a list of friends from Facebook (name and id)
and a FriendInfo Class that takes the id and gets all the info about this friend.
I thought I'd do it this way:
Create an object of FriendsManager let it get all my friends (not really a problem);
in the FriendsManager create an instance of FriendInfo;
give it the id and let it get all the info I need including geocoding of hometown;
save all this with core data.
But then where do I release this object?
In Order to get all the friends info I would create these objects in an loop that goes through my Array with friend ID's.
I also do all the getting info & geocoding with Grand Central Dispatch so do not really know when a FriendInfo got all the data it needs and is ready.

Answer 1

A Core Data object is usually a subclass of NSManagedObject, not a NSObject. You don't alloc or release it, you create one with the ManagedObjectContext and you either save or delete it but you don't release it because you don't own it.
A NSObject (prior to ARC) follows the usual rules of memory management - simply, if you get it through alloc, copy or a method starting with new, it is yours and you need to use release when you no longer use it. If you get it without allocating it - for example "NSString *string = [NSSTring stringWithFormat:#"test"]; then it is autoreleased and you don't need to release it.
Trust the analyser - shift-command-B.
Sounds like you might want to define your core data model and then create a NSManagedObject subclass for the friends information. You would create it using something like [NSEntityDescription insertNewObjectForEntityForName:#"FriendInfo" inManagedObjectContext:moc]; rather than [[FriendInfo alloc] init] as you would if it were a NSObject. The shift in thinking is that the object is created and managed by the ManagedObjectContext before you put any data in there, you request a new one and put in the data, then inform the ManagedObjectContext what you want done with that object - save or rollback (reverse all changes since the last save).

Answer 2

The problem you explain is rather "high-level" and it is difficult to give concrete advice. But in general you might want to just use ARC and don't hassle with most of these memory management problems you mentioned.
Also since you mentioned that you want to use core data, you would not release any of the objects you want to save since core data saves all objects of the context and so they never get "freed" anyway.
Your suggested approach about using a GeneralManagerClass to retrieve all the info and fill new instances of friends is generally OK. I also do it this way and it makes thinks relatively easy.
So I would just start with it and then ask more concrete questions. For now, I really don't see any general difficulty in the issues you mentioned if you follow the route you suggested...