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Re: Enabling undo in a CoreData app?
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Re: Enabling undo in a CoreData app?


  • Subject: Re: Enabling undo in a CoreData app?
  • From: Jim Correia <email@hidden>
  • Date: Sat, 29 Apr 2006 19:54:57 -0400

On Apr 29, 2006, at 7:13 PM, email@hidden wrote:

Well, it's an app that interracts with Flickr, so updating the local store only has meaning if I also pass those changes back to Flickr. And that's support that I'm adding right now. So, I really do need to prevent undo of database changes - as I fetch data from Flickr periodically or based on user actions and then do all my inserts, I don't want the user to undo that.

The list of events where the user actually makes a meaningful change and should be able to undo it is currently very small compared to all the changes and machinations that the app goes through without the user.

One thing you may wish to consider, rather than trying to wrangle the undo manager, is to use separate managed object contexts. The user does all the work in one context, and all the automated Flickr stuff happens in another. You can listen for the MOC saved notification to synchronize the MOCs. (Or it may just be appropriate to reset the Flickr MOC after doing work, then saving the changes.)


Also, you probably don't want to be manually registering undo actions for CoreData operations. CoreData already manages undo, so let it. Normally it will process the pending changes at the end of the current iteration of the event loop. If you have special needs, you can trigger this manually by sending - processPendingChanges to the MOC.

This is similar to what I mentioned above - the database action on my side has no meaning without associated web service calls. Those calls are not currently 100% built into my model (and I don't think I want them to be), so a controller object coordinates this. When an "add" happens, the controller enables undo, makes the changes in the coredata store, and generates the appropriate web services. Then it disables undo again.

Just beware that unless you send -processPendingChanges yourself, CoreData is going to do that at the end of the current event loop. This is when CoreData will post changes to the undo manager, and that is outside of your disable/enableUndoRegistration calls.
Additionally, if I take out ALL the disableUndoRegistration calls, I still don't get an enabled Undo menu item - no matter how much I change my store. And I can ask the undo manager whether undo registration is enabled, and it replies with YES.

This sounds like a responder chain problem, unrelated to the rest of your undo manager wrangling.


JIm
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  • Follow-Ups:
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References: 
 >Enabling undo in a CoreData app? (From: email@hidden)
 >Re: Enabling undo in a CoreData app? (From: Jim Correia <email@hidden>)
 >Re: Enabling undo in a CoreData app? (From: email@hidden)

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