Re: "No Selection" in Core Data
Re: "No Selection" in Core Data
- Subject: Re: "No Selection" in Core Data
- From: Chris Hanson <email@hidden>
- Date: Sat, 25 Jun 2005 20:24:01 -0700
On Jun 25, 2005, at 10:27 AM, J Tichenor wrote:
I'm sure there is an easy answer to this: I have two Entities, one
is a single Budget entitiy and then any number of user added
EffectUnits in relation to the budget.
It's always very useful to distinguish between entities (descriptions
of the types of things in your application) and instances of entities
(the things themselves). So in your model, you have two entities,
Budget and EffectUnit. You have a one-to-many relationship between
Budget and EffectUnit, so one Budget instance can be related to any
number of EffectUnit instances.
Once everything is wired up, I can add EffectUnits without issue,
but the properties of Budget show up as No Selection in it's
relevant fields.
Are you creating an instance of Budget?
I'm sure it has something to do with not properly instancing the
Budget Entity when the program launches -- I guess my assumption as
a programmer is that the Budget entity should automatically
instance when the program starts as it must exist
It sounds like you're not creating an instance of Budget. The
framework has no way of knowing that a Budget instance "must" exist
-- that's an application-level decision. After all, it may be
perfectly valid in your application to have a document containing no
Budget instances, or to have a document containing fifty Budget
instances.
-- but I don't know how to instance the Budget and where --
probably in AppDelegate, right? Maybe in managedObjectContext? I've
tried to find the spot but must admit the autogenerated code
doesn't necessarily make itself apparent...
The template code is just a starting point. What you probably want
to do is check the contents of the persistent store after adding it
to your application's coordinator. Then if it contains no Budget
instances, create an initial one and configure it as appropriate.
Where exactly you would do this depends on what type of application
you're building (document-based or other) but the way you would do so
is the same.
-- Chris
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