How to objects from a fetchedResultsController to a Plist? - cocoa

Question

Can someone help me. I have a coredata application but I need to save the objects from a fetchedResultsController into an NSDictionary to be used for sending UILocalNotifications.
Should I use an NSMutableSet, or a NSDictionary, or an array. I'm not used to using collections and I can't figure out the best way to do that.
Could you please give me clues on how to do that please ?
Thanks,
Mike

Answer 1

If I'm reading your question correctly, you're asking how you should pack objects into the userInfo dictionary of a UILocalNotification. Really, it's however works best for you; userInfo dictionaries are created by you and only consumed by you.
I'm not sure why you would be using an NSFetchedResultsController - that class is for managing the marshaling of managed objects between UI classes (like UITableView) efficiently, whereas here it sounds like you would be better off just getting an NSArray of results from your managedObjectContext and the corresponding request, like this:
NSError *error = nil;
NSArray *fetchedObjects = [myManagedObjectContext executeFetchRequest: myRequest error: &error];
if (array == nil)
{
// Deal with error...
}
where you have a pre-existing managed object context and request. You don't need to use an NSFetchedResultsController here.
From there, the simplest suggestion would be to build your userInfo dictionary like this:
NSDictionary* myUserInfo = [NSDictionary dictionaryWithObject: fetchedObjects forKey: #"AnythingYouWant"];
UILocalNotification *localNotif = [[UILocalNotification alloc] init];
// ... do other setup tasks ...
localNotif.userInfo = myUserInfo;
[[UIApplication sharedApplication] scheduleLocalNotification:localNotif];
[localNotif release];
Then when it comes time to receive that notification, you can read that dictionary like this:
- (void)application:(UIApplication *)app didReceiveLocalNotification:(UILocalNotification *)notif
{
NSArray* myFetchedObjects = [notif.userInfo objectForKey: #"AnythingYouWant"];
for(id object in myFetchedObjects)
{
// ... do other stuff ...
}
}
Now, hopefully that's clarified how the userInfo dictionary works. I don't know the details of your app, so it's hard to say, but I'm suspicious that actually passing fetched objects is NOT what you want to do here, mainly because I'm not sure that you have any guarantee that the receiving delegate method will be working with the same object context as the sending method. I would suggest perhaps putting the entity name and predicate in the dictionary and then refetching the objects at receive time with whatever the current MOC is at that moment.
Good luck!