This is what I have used for years with good success:
- (BOOL)retainedObjectHasBeenDeleted
{
// if object has been deleted, then it no longer exists
if ([self isDeleted]) return YES;
// otherwise, see if object with this ID exists in the database
NSManagedObjectContext *context = [self managedObjectContext];
if (context == nil) return YES;
NSManagedObjectID *objectID = [self objectID];
if (objectID == nil) return YES;
NSManagedObject *obj = [context objectRegisteredForID:objectID];
return obj == nil;
}
I'm currently experimenting with the following to see if it's as safe and
perhaps faster:
- (void)prepareForDeletion
{
// track object deletion for faster testing below
NSString *objIDStr = [[[self objectID] URIRepresentation]
resourceSpecifier];
[_deletedObjectIDs addObject:objIDStr];
}
- (BOOL)retainedObjectHasBeenDeleted
{
NSString *objIDStr = [[[self objectID] URIRepresentation]
resourceSpecifier];
return [_deletedObjectIDs containsObject:objIDStr];
}
Unfortunately _deletedObjectIDs grows without bound. So you wouldn't want to
use this approach if you are expecting a lot of deletions.
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