On Dec 31, 2008, at 4:46 AM, Quincey Morris wrote:
I don't see how trying to do this in - writeToURL:ofType:forSaveOperation:originalContentsURL:error: is ever going to work.If you are given (basically) an old and new package location, then you're forced to copy everything:-- Trying to write changed files in the old location would be a really bad idea.-- Moving the unchanged files from the old location to the new location would probably work (if the save operation is a pure save, not a save-as or save-to), but would be a really bad idea if there was an error during the save (because the contents of the new location would presumably get thrown away).The *real* question here is: what's a *safe* strategy for saving a package by changing parts of it? You really need a single atomic operation to commit the changes, and most file systems don't provide this for an arbitrary set of files. NSDocument's answer is that there isn't a safe strategy, so it always saves by creating a copy. (And even that's not perfectly safe if the file system doesn't provide the equivalent of FSSwapFiles.)Using Core Data as the storage mechanism for blobs of data is a possibility, but it's also a PITA because:-- you likely need to turn off NSPersistentDocument's undo handling and provide your own-- Core Data doesn't have save-to, and its save-as sucks (does a store migration)-- if you have a lot of data, Core Data is going to keep copies of much of it in internal cachesMy suggestion would be to go ahead and use a package document format, and to copy the unchanged files, and see how long it takes. If the save times are unacceptable, then a database solution (not Core Data) is probably the next step.
Thanks for the pointers, I'll think about that. It's rather surprising that NSDocument's save-as-copy-and-move strategy that works so well for single files backfires so heavily in my case.
Regards Markus -- __________________________________________ Markus Spoettl
smime.p7s
Description: S/MIME cryptographic signature
_______________________________________________ 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
