On 2011-01-22, at 8:34 PM, Kenneth Baxter wrote: > Thanks Dave. I am now trying to use an array controller. I have set up the > array controller and an observer on arrangedObjects, and that gets called > during my addition and removal of children, but the change kind is always 1, > and there is never anything in the old or new value arrays, so nothing beyond > this knows whether it was an insertion or a deletion. I'm not sure exactly > how much use that is in managing my other objects.
Looking back at my code, I see that I just use the KVO message to know that something changed. I then re-traverse the data model to update the view. (Not the most scalable technique.) > The other things that need to remain in sync during undo and redo are not > other nodes - they are some things that are managed at the view and > controller layers of the application. I have some background threads that are > processing data and need to know when a node is removed, and I have a mapping > between the data and a number of front end objects and views, some of which > may be animating at the time, as well as an intermediate model layer, and if > any of those objects try to access the core data objects when they have been > deleted, then all hell breaks loose. Therefore I have been sending > notifications before the nodes are removed so that the processing thread can > pick up on that and remove the node from the ones it is working on, and the > animations can have their connections to the back end and other related > objects cleaned up nicely. I don't know how else to accomplish a nice tidy > up, since the animations and processing are using other threads, and may try > to access the deleted node. If your background thread can copy the necessary data, then it doesn't have to worry about it disappearing. My understanding is that accessing a potentially changing MOC from another thread is problematic at best. See Ben Trumbull's posts on this topic. Ex. March 16, 2007 Re: Core Data & threads [re: Ping: Look for hints for "nested transaction" problem with Core Data] The usual pattern seems to be to have a separate MOC for the background thread and echo changes to it when the MOC in the main thread changes (NSManagedObjectContextObjectsDidChangeNotification). _______________________________________________ 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
