Question

I’ve had an app that I’ve been working on for a while that I originally included Core Data support in, but didn’t actually start trying to use it until recently. Now that I’m actually trying to use Core Data … it doesn’t seem like I can. When I edit my xcdatamodel to include new (or really, any) entities, I can’t seem to actually access those entities in the application itself. Somewhere along the way, I renamed the project from ProjectTest to CoreDataTest, which I suspect is causing or is related to this problem. I haven’t changed any of the default methods which were generated in the app delegate initially by Xcode (initially 3, but now using 4).

So, I’ve created a new entity called simply enough TestEntity with a single attribute (String) TestAttribute.

In my app delegate, I’ve tried a couple of different ways to access the Entity and save a string to it, but all fail. So I thought I’d walk through all entities thinking I was somehow messing up creating the creation of the NSEntityDescription. I put the following code in to show a listing of all Entities … and got nothing:

NSManagedObjectModel *model = [[self.managedObjectContext persistentStoreCoordinator]
                               managedObjectModel];
NSLog(@"List of Entities:");
for (NSEntityDescription *entity in model)
{
  NSLog(@"Entity: %@", entity);
}
NSLog(@"Done with list");

For an output I just get:

2011-09-21 14:58:01.955 CoreDataTest[1813:b603] List of Entities:
2011-09-21 14:58:01.955 CoreDataTest[1813:b603] Done with list

So … I’ve tried cleaning the build. I’ve searched through a lot of questions here on SO and more on google, but I can’t seem to find anything that solves my problem. I don’t get any actual error messages or uncaught exceptions during a run of the app. Any ideas what could be causing it? I’m sure it’s probably something stupidly simple that I’m overlooking …

Thanks for any help,

Will

Answer 1

Try adding .entities, i.e.:

for (NSEntityDescription *entity in model.entities) { //...

See The docs for NSManagedObjectModel.

Also check your model is not null. Try printing it: NSLog(@"%@",model);