On Dec 31, 2008, at 12:57 AM, Kyle Sluder wrote:
On Wed, Dec 31, 2008 at 3:51 AM, Markus Spoettl <msappleli...@toolsfactory.com> wrote:My app stores a lot of data in a document, potentially hundreds ofmegabytes. The problem with using single files and NSKeyedArchiver is that one has to write everything, even if only a tiny part of the structure changed. My data is clustered into handy little pieces which could be savedinto their own separate files within the package.Have you thought of using Core Data instead? This is what the SQLite store is designed to address.
No I have not, but I have a feeling that it wouldn't be suitable. The data I store contains (when the document is big) millions of double values (amongst other things) spread across hundreds of thousands of objects. If the performance of NSKeyedArchiver is any indication the system wouldn't scale very well. It is an assumption and it might be totally wrong but I guess the overhead of keyed archiving is significantly less than that of Core Data.
The problem is that - if I understand it correctly - when using file wrapper -fileWrapperOfType: of NSDocument, I always have to provide the complete wrapper, including all contained wrappers. That of course is exactly what I hoped to avoid because it means I'd have to write all data (this time intoseparate files/wrappers).That is correct. You have to implement -readFromURL:ofType:error: and -writeToURL:ofType:forSaveOperation:originalContentsURL:error: if you want to go the document-package route and not wind up with wholesale writing. This means, of course, that you need to be able to tell what has changed in the document, and then be able to determine which fragments need to be updated on disk.
That's no problem, that information is available. The documentation for -writeToURL:ofType:forSaveOperation:originalContentsURL:error: states:
----------The value of absoluteURL is often not the same as [self fileURL]. Other times it is not the same as the URL for the final save destination. Likewise, absoluteOriginalContentsURL is often not the same value as [self fileURL].
----------which is a little problem because to update my packages I need to original location. Do you have any insights as to what "often not the same" in this context might mean? To write the diff into the package I'd have to have access to the package. It doesn't sounds as it that's guaranteed.
Regards Markus -- __________________________________________ Markus Spoettl
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