Re: How to Versions Browser when document won't open?
Re: How to Versions Browser when document won't open?
- Subject: Re: How to Versions Browser when document won't open?
- From: Jerry Krinock <email@hidden>
- Date: Fri, 21 Mar 2014 00:15:59 -0700
It looks like we have a solution to the problem of the user not being able to restore a corrupt document from Versions Browser because the document is corrupt, and so she can’t open it, and so she can’t File > Revert to > Browse All Versions.
The solution is:
• Override -[NSDocument openDocumentWithContentsOfURL:display:error:].
• After invoking super, look in returned error for SQLite error code:11, 'database disk image is malformed’.
• If that error is found, clear all data from the document on the disk.
• In its place, copy in data from a good, empty document.
• Invoke super again. The document will open this time.
• Display a sheet informing user that document was corrupt and suggest File > Revert to > Browse All Versions.
I’ve not written the code yet, just done the above manually with a Core Data SQLite document that has legacy Delete/Rollback journaling. Corruption was simulated by punching out the middle of the file with a hex editor. I also used a hex editor to nuke and pave the document. Result: Versions Browser showed previous versions of the corrupted document, as desired. After restoring one, I was able to edit, save, close, and re-open it and nothing complained.
Happily, no reverse engineering of /.DocumentRevisions-V100 was necessary, but I’m still open to any better ideas. Did I miss an easier solution to this problem that is built into Cocoa?
I’m aware that the magic in NS(Persistent)Document often comes back to bite with a vengeance days or weeks later. I shall post again if I have any trouble.
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