Objects not being removed from NSOutlineView/ManagedObjectContext - objective-c

Question

I have an NSTreeController that is getting objects adding to it addObject: method.
I have an NSOutlineView which has its content bound to the NSTreeController's arrangedObjects.
When I delete an object, as below
- (void) deleteSelectionConfirmed {
id selectedItem = [_outlineView itemAtRow:[_outlineView selectedRow]];
id obj = ((NSTreeNode *)selectedItem).representedObject;
NSManagedObjectContext *context = [self managedObjectContext];
[context deleteObject:obj];
NSError *error;
NSLog(#"%hhd", [[self managedObjectContext] hasChanges]);
if (![context save:&error]) {
NSLog(#"Whoops, couldn't save: %#", [error localizedDescription]);
} else {
NSLog(#"%#", [_hostController content]);
[_outlineView reloadData];
}
NSLog(#"%hhd", [[self managedObjectContext] hasChanges]);
}
It doesn't seem to be deleted.
The print out of my treeController content looks as such.
"<Host: 0x6080000b41c0> (entity: Host; id: 0x608000034180 <x-coredata://6E3284F6-D870-4DAF-A4E5-B6A4EB75021E/Host/p131> ; data: {\n hostname = asdfasdf;\n index = 0;\n children = \"<relationship fault: 0x60800022ecc0 'children'>\";\n title = gggg;\n username = asdf;\n})",
"<Host: 0x6080002a0960> (entity: Host; id: 0x608000032a80 <x-coredata://6E3284F6-D870-4DAF-A4E5-B6A4EB75021E/Host/p133> ; data: <fault>)"
)
The second line is the 'deleted' object. This is causing issues with the NSOutlineView to display a blank row. If I close an re-open my app however, dumping an NSFetchRequest shows my Managed object was actually deleted, and my NSOutlineView has the intended rows.
Am I missing something? Am I adding objects the wrong way? Should i be using a different binding? Any help is greatly appreciated.

Answer 1

Set the tree controller to automatically prepare its content (using the moc, the entity name, and the fetch predicate). If you do that, you presumably want to remove that code from -applicationDidFinishLaunching:.
From Core Data Programming Guide: Troubleshooting Core Data:
Table view or outline view contents not kept up-to-date when bound to > an NSArrayController or NSTreeController object
Problem: You have a table view or outline view that displays a
collection of instances of an entity. As new instances of the entity
are added and removed, the table view is not kept in sync.
Cause: If the controller's content is an array that you manage
yourself, then it is possible you are not modifying the array in a way
that is key-value observing compliant.
If the controller's content is fetched automatically, then you have
probably not set the controller to "Automatically prepare content."
Alternatively, the controller may not be properly configured.
Remedy: If the controller's content is a collection that you manage
yourself, then ensure you modify the collection in a way that is
key-value observing compliant—see “Troubleshooting Cocoa Bindings”.
If the controller's content is fetched automatically, set the
"Automatically prepares content" switch for the controller in the
Attributes inspector in Interface Builder (see also
automaticallyPreparesContent). Doing so means that the controller
tracks inserts into and deletions from its managed object context for
its entity.
If neither of these is a factor, check to see that the controller is
properly configured (for example, that you have set the entity
correctly).
So, the tree controller does not track insertions into and deletions from the managed object context unless it is set to automatically prepare content.