One way to do this through the MVC paradigm is to bind an NSArrayController or
NSTreeController to your managed object context (in Entity mode), and then have
your view layer bind or use KVO with the selectedObjects or arrangedObjects
attribute of the controller.
On 2011-01-21, at 7:03 PM, Kenneth Baxter wrote:
> I am trying to work out an issue with undo in a few places in my application,
> and think if I "get it" with one of the places, I should be able to apply the
> same theory elsewhere.
>
> I have a parent and children relationship, and need to have a few things
> happen during the process of adding and deleting a child so that the rest of
> the application stays in sync. The core data side of things manages the
> undoability of the data, but of course it doesn't know how to send the other
> messages at the right times, so I have tried to add the notification messages
> in the reverse order on the undo stack (prepareWithInvocationTarget), but
> then redo doesn't work properly All the undo and redo for the rest of my
> application is working fine (just fairly simple relationships and
> attributes), but I think there's a design pattern I'm missing here for the
> more complex case.
>
> It's probably best for me to just post the things that need to happen during
> a normal add of a child and deletion of a child, and hopefully someone will
> be able to give me guidance on how to make it undoable and redoable.
>
> - (MyNode *)createChild {
> MyNode *child = [NSEntityDescription
> insertNewObjectForEntityForName:@"MyNodeEntity" inManagedObjectContext:[self
> managedObjectContext]];
>
> // Set a bunch of properties on the new child.
> ...
>
> [[self mutableSetValueForKey:@"children"] addObject:child];
>
> // Set a bunch more properties on the new child and other core data
> managed objects
> ...
>
> // Let the front end of the application know about it
>
> [[NSNotificationCenter defaultCenter]
> postNotificationName:@"ChildNodeAddedNotification" object:... userInfo:...];
>
> return child;
> }
>
>
> - (void)deleteChild:(MyNode *)aChild {
> NSArray *affectedChildren = [aChild selfAndAllDescendants];
>
> [[NSNotificationCenter defaultCenter]
> postNotificationName:@"NodesWillBeRemovedNotification" object:self
> userInfo:[NSDictionarydictionaryWithObjectsAndKeys:affectedChildren,
> @"affectedChildren", nil]];
>
> [[self mutableSetValueForKey:@"children"] removeObject:aChild];
>
> if (self.parent) {
> // Do some things that could affect some ancestor values
> ...
> }
>
> for (MyNode *tn in affectedChildren) {
> // Do some special processing to clean up things that might be
> pointing to the descendants
> ...
> // Set a non-persistent property on the tn node which will be
> picked up by KVO to show that the node will be removed, so we can kill
> observing etc.
> ...
> [[self managedObjectContext] deleteObject:tn];
> }
> aChild.parent = nil;
>
> // Do some post-processing to make sure some other values are kept in
> sync.
> ...
>
> // Post a notification so the front end can be updated.
> [[NSNotificationCenter defaultCenter]
> postNotificationName:@"NodeRemovedNotification" object:self
> userInfo:[NSDictionarydictionaryWithObjectsAndKeys:aChild, @"node", self,
> @"parent", affectedChildren, @"affectedChildren", nil]];
> }
>
>
> I have looked at some of the previous posts on related things, but haven't
> seen an answer that would explain what to do for this kind of thing (and some
> posts were suggesting turning off core data's undo completely and doing your
> own etc, which would not be good for me since I have a *lot* of places where
> it is working just fine for me and only about 6 places where it's not).
>
> Thanks in advance for any advice on this.
>
> Ken
>
> _______________________________________________
>
> Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
>
> Please do not post admin requests or moderator comments to the list.
> Contact the moderators at cocoa-dev-admins(at)lists.apple.com
>
> Help/Unsubscribe/Update your Subscription:
> http://lists.apple.com/mailman/options/cocoa-dev/dave.fernandes%40utoronto.ca
>
> This email sent to dave.fernan...@utoronto.ca
_______________________________________________
Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
