Re: Data Model Design Q: Translation [Resolved]
Re: Data Model Design Q: Translation [Resolved]
- Subject: Re: Data Model Design Q: Translation [Resolved]
- From: Ben Lachman <email@hidden>
- Date: Tue, 18 Jul 2006 02:09:13 -0400
Actually, I was looking for something a little more complicated.
I ended up solving my problem manually. I had originally wanted two
relationships from my translation object to the two objects being
translated. I also wanted these to be inverse relationships so
CoreData could make everything happen magically. However, it doesn't
seem that the data modeler can create two inverse one to many ( <---
>> ) relationships to the same entity.
What I ended up doing was creating three relationships: one to-many
relationship from the entity to be translated to the translation
entity, and then two to-one relationships from the translation entity
back to the original entity. I then wrote some glue code to manage
updating the to-many relationship (couple additions to setValue,
deletion handling, and a addValue:forCollectionWithKey: method). The
result of all this is that I can now translate back and forth between
two objects (such as coins or anything else that has a name and
amount substitution scheme) based on a dynamic list of translation
entities.
->Ben
On Jul 12, 2006, at 4:00 PM, I. Savant wrote:
Ben:
Nobody's responded yet so I'll take a stab. If all you're asking
is how to create entities with the relationships you've described
in your ASCII graphic below, then this is very basic and simple
with the data modeler.
If you require a "Coin" of a certain type to match a certain set
of criteria to be allowed to be related to a substitution (or vice-
versa), you will need to implement validation with whatever logic
you choose.
All of how-to's of this can be read here:
http://developer.apple.com/documentation/Cocoa/Conceptual/CoreData/
index.html
For information on how to use the modeler, see XCode's help book.
If I've missed your point, you'll probably need to elaborate.
On Jul 11, 2006, at 4:38 PM, Ben Lachman wrote:
I'm wondering how to design my data model so that I can include a
substitution/translation object in my model. Basically I want an
object that says 3 of this thing is equal to 4 of that thing,
where the things are of the same class. A basic example would be
substituting change: 5 pennies are equal to 1 nickel, 4 nickels
are equal to 2 dimes, etc. The inverse of these is always true as
well. This makes sense and seems pretty simple, but I can't
figure out a decent way of doing this within the xcode data
modeler. What I'd like is something like this:
[ Coin ] <---->> [ Substitution ] <<----> [ Coin ]
where [ Coin ] has a substitutions to-many relationship and
[ Substitution ] has a pair of amounts (5 and 1 for instance) and
relationships (to the nickel and penny coin objects).
Does anyone have an idea of how to do this in xcode?
Thanks,
->Ben
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