Re: core data - delete of object.
Re: core data - delete of object.
- Subject: Re: core data - delete of object.
- From: Ashley Clark <email@hidden>
- Date: Tue, 18 Nov 2008 15:39:40 -0600
That's true, processPendingChanges is used by the context to implement
undo functionality but there's no reason why you can't call it
yourself after your delete since you've disabled the context's undo
functionality.
Here's an example where events is an NSArrayController:
- (IBAction)deleteEvent:(id)sender {
NSManagedObjectContext *context = [self managedObjectContext];
if ([events selectedObjects] && [[events selectedObjects]
count]) {
[context deleteObject:[[events selectedObjects]
objectAtIndex:0]];
[context processPendingChanges];
}
}
Or add a category to NSManagedObjectContext:
- (void)AC_deleteObjectAndProcessPendingChanges:(id)object {
[self deleteObject:object];
[self processPendingChanges];
}
Why disable the undo functionality at the context level though? If
you're providing your own undo support elsewhere there's nothing that
I know of that says you have to use the context's undoManager
elsewhere. If you have sections of code that you don't want to be
undoable you can still call disableUndoRegistration and
enableUndoRegistration on the context's undoManager itself too (as
long as you don't want any objectsDidChange notifications during that
block).
Ashley
On Nov 18, 2008, at 6:44 AM, John Clayton wrote:
I guess processPendingChanges is only called if there is an
undoManager? Correct? I don't have one - I disabled it intentionally.
I've tried that notification, its only fired on save of the context.
On 18/11/2008, at 1:22 PM, Ashley Clark wrote:
According to the documentation and to my quick test, the
NSManagedObjectContextObjectsDidChangeNotification is sent during
processPendingChanges. At the very least that happens at the end of
every event loop automatically. Even if you've bypassed your event
loop somehow you can still call processPendingChanges on your
context yourself after your object deletion and have it do whatever
extra processing you need.
ie.
NSManagedObjectContext *context = [theObject managedObjectContext];
[context deleteObject:theObject];
[context processPendingChanges];
Ashley
On Nov 18, 2008, at 12:54 AM, John Clayton wrote:
Thanks Jim, unfortunately all occur either at pre-save or save
time, which is too late.
I'm basically looking to restore some state on an object at time
of deletion, e.g.
if A is associated with B via a to-many relationship from A->B,
then when one instance of B is deleted - we need to change a
property on A.
On 17/11/2008, at 10:59 PM, Jim Correia wrote:
On Nov 17, 2008, at 4:51 PM, John Clayton wrote:
I'm using core-data and need to know when a particular core-data
object (derived from NSManagedObject of course) is about to be
deleted. I'm deleting objects simply by using the managed
object context's deleteObject method, like this:
[[theObject managedObjectContext] deleteObject:theObject];
Is there a way to be notified immediately of the delete? I need
to know immediately, not only when the context is saved. Am I
missing something painfully obvious here?
now, I could of course put a 'deleteThisObject' method onto the
class I'm deleting, but isn't there a core-data way to handle
this?
I've tried catching the
NSManagedObjectContextObjectsDidChangeNotification notification
- but that only fires on context saves, same with the
willTurnIntoFault method as well as the dealloc - all these
methods are only ever called when the context is being saved -
which in my case is (a) unpredictable, (b) too late .
Is -validateForDelete: time too late? If not, that's an option.
You can also try
[context deleteObject: object];
[context processPendingChanges];
... handle notification ...
[context save: &error];
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