Hey all,
I'm fairly new to iPhone/Cocoa, and brand new to Core Data. I'm in the
process of writing a data manager, and I would like it to use Core Data.
Unfortunately my brain is breaking a little bit with a conceptual issue. I
need an entity which will store some binary data along with a guid (a 16
byte int) for indexing/lookup. This in itself is a little bit harrowing,
since I don't see any native support for 16 byte ints in Core Data.
To make matters worse though, the guid is wrapped in what is effectively a
container class which includes network serialization functionality, an
isEqual method, etc along with the 16 bytes of guid data. If possible I
would like to store the wrapper object in Core Data rather than extracting
data from it and then rebuilding it each time I store/retrieve the object.
It seems eminently possible to do the actual storage/retrieval using an
NSValueTransformer with a Transformable attribute, but what is hurting my
brain is the idea of lookups. How (if at all) can I store these wrapper
objects in such a way that I can do fetch requests based on their internal
values?
That is, if I have an object:
wrapperA:
guidBytes "1111222233334444"
And I have already stored two entities in Core Data with something like
EntityInstanceA:
binaryData: foo
accessDate: bar
guidInstance:
guidBytes: "1111222233334444"
EntityInstanceB:
binaryData: baz
accessDate: quz
guidInstance:
guidBytes: "4444333322221111"
Is it possible for me to do a fetch request using the guidBytes inside
wrapperA to return me EntityInstanceA with its matching guidBytes, which are
stored as a member of a class which is "blobbed" into an entity attribute?
Wow, I hope that all makes sense.
Possible solutions I have now are
- to save the guid bytes as an additional string attribute in the entity and
just key off that (like an id column) but that seems like it's storiing
extra data.
- to not save the wrapper object at all, just the inner byes, and rebuild
the wrapper each time I do a fetch, but that seems less efficient than I
would like and means i can't just return the fetched entity to the requestor
without also returning one of the wrapper objects.
Ideas? Suggestions? Rollings of eyes? Pitchforks and torches?
_______________________________________________
Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
