Upgrading NSDocument format, best practice
Upgrading NSDocument format, best practice
- Subject: Upgrading NSDocument format, best practice
- From: Markus Spoettl <email@hidden>
- Date: Wed, 16 Sep 2009 15:52:16 +0200
Hello,
I have an NSDocument that reads old-format files which it does no
longer write. When loading such an old format file, the app warns the
user about the format-change and the fact the file can't be read by
older versions once saved with the new one.
Unfortunately, producing files in a compatible format is not possible.
I know...
The problem is most warning messages are quickly dismissed unread. So
in order to avoid that the user accidentally overwrites old-format
files he wanted to keep, I make sure the he has to pick a filename
when he decides to save the freshly upgraded document.
To do so I set -fileURL to NIL and tell the document it has been
loaded from a different file using -updateChangeCount:
- (BOOL)readFromData:(NSData *)data ofType:(NSString *)typeName error:
(NSError **)outError
{
[... read data and upgrade if necessary ...]
if (thisWasAnOldFormat) {
[self setFileURL:nil];
[self updateChangeCount:NSChangeReadOtherContents];
}
}
This works exactly as expected, the file is unnamed and changed, so
whatever happens a filename must be chosen. The user would clearly
prefer a solution more transparent than this, but I'd rather not
convert data he's not willing to upgrade just yet.
I guess my question is, is this the way to do it? Are there
alternatives?
Regards
Markus
--
__________________________________________
Markus Spoettl
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