Core Data "Save as" versions
Core Data "Save as" versions
- Subject: Core Data "Save as" versions
- From: Ken Tabb <email@hidden>
- Date: Thu, 11 Sep 2008 10:09:57 +0100
Morning folks,
I was reading the Core Data version migration documentation, and it
seems easy to use (haven't put it into practice yet as I was reading
it on a sunbed on hols, and I have enough trouble sneaking programming
books into the shared luggage, let alone the laptop etc.).
The docs are understandably written from a "how do I upgrade user's
software version without wrecking their existing data" perspective,
but I was wondering if:
[1] The same model migrations can be used to save documents as a
previous version format (eg. save a file from v2.app as v1.xml format
instead of v2.xml format, so they can send stuff to their mates who
use the older version). Obviously assuming they don't mind losing the
"new features" that won't be in v1.xml.
[2] on a related note, if it's possible to generally save documents as
sqlite (for compression purposes / atomic saving benefits etc.) but
offer a "save as XML" type feature, so that your file format can be
used by other apps. Or am I going about this the wrong way / might the
XML file format change internally between Core Data revs, thus
breaking any file reading ability other apps might have for my app's
files?
Or for [2] would I be "better off" rolling my own text-based file
format ([self twitch]) so that Core Data's internal SQL / XML formats
can change without affecting my documents' readability in other apps?
Put another way, how do you go about having a Core Data doc-based app
that can't be accused of having a proprietary (i.e. unreadable) file
format as its native file format? That's not a criticism, just an
innocent question!
I have tried to read all the Core Data docs I could find, so apologies
if I've missed the obvious.
Thanks in advance for any light you can shed,
Ken
- - - - - - - - - -
Dr. Ken Tabb
Mac & UNIX Developer - Health & Human Sciences
Machine Vision & Neural Network researcher - School of Computer Science
University of Hertfordshire, UK
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