NSPersistentDocument's metadata APIs, when can I set my metadata before saving?
NSPersistentDocument's metadata APIs, when can I set my metadata before saving?
- Subject: NSPersistentDocument's metadata APIs, when can I set my metadata before saving?
- From: "Sean McBride" <email@hidden>
- Date: Mon, 2 Jun 2008 12:58:37 -0400
- Organization: Rogue Research
Hi all,
I am trying to make use of NSPersistentDocument's metadata APIs. I'm
having trouble with the 'when' more than the 'how'.
Which method of the saving process should I override to call
setMetadata:forPersistentStoreWithURL:error:?
All the metadata APIs want the NSURL of the store, which seems to be a
problem when a document is saved the first time.
<http://developer.apple.com/documentation/Cocoa/Conceptual/
NSPersistentDocumentTutorial/07_Metadata/chapter_8_section_4.html#//
apple_ref/doc/uid/TP40002835-SW11> says: "When a document is saved, Core
Data calls the NSPersistentDocument method
writeToURL:ofType:forSaveOperation:originalContentsURL:error:. You can
override this method to add metadata to the new store before it is
saved." The sample overrides the method and first does:
if ([self fileURL] != nil)
[self setMetadataForStoreAtURL:[self fileURL]];
but 'fileURL' returns nil when a document is being saved for the first
time. If I try using the URL passed in writeToURL I get the exception
"*** -metadataForPersistentStoreWithURL:error: cannot be sent to an
abstract object of class NSPersistentStore: Create a concrete instance!"
Thanks,
--
____________________________________________________________
Sean McBride, B. Eng email@hidden
Rogue Research www.rogue-research.com
Mac Software Developer Montréal, Québec, Canada
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