On Apr 16, 2009, at 10:04 PM, David Zwerdling wrote:
A while ago I wrote a simple application in which users create and
manipulate CoreData entities named "DataSets".
It is good to use the appropriate terminology.
Users don't "create and manipulate CoreData entities"; you define the
entities via the managed object model. Users then create and
manipulate managed objects.
Typically entity names are in the singular, and describe the type of
thing they represent.
I used the document preset so I didn't have to deal with any of the
file writing stuff.
It's not clear exactly what you mean here, but judging by the next
code fragment you appear to be abusing the document architecture.
Assuming this is the case, it doesn't really help, and since the basic
Core Data application template contains all the "file writing stuff"
you need, doesn't save you much anyway.
Anyways, I'm writing a new application that uses these data sets.
Users save the file from the prior application and can "import" data
sets into this new application. At least, hypothetically at this
point. The issue is, when using code like this (url points to a
document full of data sets):
NSPersistentDocument *pd = [NSPersistentDocument new];
BOOL success = [pd configurePersistentStoreCoordinatorForURL:url
ofType:NSXMLStoreType modelConfiguration:nil storeOptions:nil
error:&error];
NSSet *ros = [[pd managedObjectContext] registeredObjects];
Following on from the preceding, it's not clear why you're creating a
persistent document.
Is this to be presented to the user?
success comes back true, but there are no managed objects in 'ros'.
At this stage, you haven't fetched any objects:
"The framework tries to be as efficient as possible. Core Data is
demand driven, so you don't create more objects than you actually
need. The graph does not have to represent all the objects in the
persistent store. Simply specifying a persistent store does not bring
any data objects into the managed object context."
<http://developer.apple.com/documentation/Cocoa/Conceptual/CoreData/Articles/cdBasics.html#//apple_ref/doc/uid/TP40001650-207422-TPXREF147
>
So, is there some sample code I can see which loads the managed
objects of an xml file? I've looked pretty exhaustively and
everything seems too high level (relying on the single-file model
that I implemented in my original application.) Am I missing
something silly?
Probably the above. It's also not clear what you mean by "everything
seems too high level (relying on the single-file model that I
implemented in my original application)".
mmalc
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