How to pass ManagedObjectContext to TabBarViewControllers - iphone

Question

After reading quite a couple of questions in stackoverflow, I still can't find an answer at the moment.
I have trouble passing ManagedObjectContext from appdelegate to my tabbarcontroller view.
in my appdelegate.m I have this
#import "memoView.h"
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
memoView *mView = (memoView *)navigationController.topViewController;
mView.ObjectContext =[self managedObjectContext];
}
in memoView.m
- (void)viewDidLoad
{
[super viewDidLoad];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:#"NoteLog" inManagedObjectContext:[self ObjectContext]];
[fetchRequest setEntity:entity];
NSError *error;
self.memoInfo = [ObjectContext executeFetchRequest:fetchRequest error:&error];
//self.title = #"Memo";
[fetchRequest release];
}
error reason: '+entityForName: could not locate an NSManagedObjectModel for entity name 'NoteLog''
I'm not sure what I have done wrong, I'm relative new to core data.
Any comments are appreciated.

Answer 1

I ran into this at one point and solved like this:
YourAppDelegate *appDelegate = (YourAppDelegate *)[[UIApplication sharedApplication] delegate];
self. ObjectContext = appDelegate.ManagedObjectContect;

Answer 2

Where do you put following code? I guess mView is nil when you assigning mView.ObjectContext:
#import "memoView.h"
memoView *mView = (memoView *)navigationController.topViewController;
mView.ObjectContext =[self managedObjectContext];

Answer 3

I'd personally implement a Singleton for my CoreData Stack. - But in a slightly safer manner like here.
The singleton pattern is basically an excuse for a "global variable". Although if implemented correctly and used wisely one of the most powerful patterns there are. Simply speaking, what it does is: It creates an object of a class IF it doesn't exist yet and stores it in a static variable of that object's class. And since a class variable's content is the same amongst all the instances of that class (obviously), the next time you try to allocate an instance of the class it checks whether it was allocated before, and if it was returns the old instance.
Thus, you can basically "allocate" from anywhere and however often you want and you'll always get the same object back.
People tend to then call that singleton class something along the lines of "DataManager" or similar.