How To Pass ManagedObjectContext To Other View Controllers in Special Case

I have a rootViewController like so:

Header:

@interface ParkingRootViewController : UIViewController {
    UINavigationController *navigationController;
    UIToolbar *toolbar;
    UIBarButtonItem *lastUpdateLabel;

    NSPersistentStoreCoordinator *persistentStoreCoordinator;
    NSManagedObjectModel *managedObjectModel;
    NSManagedObjectContext *managedObjectContext;
}

@property (nonatomic, retain) IBOutlet UINavigationController *navigationController;
@property (nonatomic, retain) IBOutlet UIToolbar *toolbar;
@property (nonatomic, retain) IBOutlet UIBarButtonItem *lastUpdateLabel;

@property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel;
@property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;

@property (nonatomic, readonly) NSString *applicationDocumentsDirectory;

-(IBAction)selectHome:(id)sender;
//-(void)loadOverlays;
-(void)testCoreData;

@end

Implementation:

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];

    //...

    [self testCoreData];

    //creating label in tool bar 
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 150.0f, 20.0f)];
    label.text = @"last updated...";
    label.textColor = [UIColor colorWithWhite:1.0 alpha:1.0];
    label.backgroundColor = [UIColor clearColor];
    label.textAlignment = UITextAlignmentCenter;
    //label.highlightedTextColor = [UIColor colorWithWhite:0.5 alpha:1.0];
    //label.highlighted = YES;
    label.font = [UIFont systemFontOfSize:13.0];
    label.userInteractionEnabled = NO;

    [lastUpdateLabel initWithCustomView:label];
    [label release];

    [self.view addSubview:self.navigationController.view];

    [self.navigationController.view setFrame:self.view.frame];

}

But I need to transfer my managedObjectModel to my table view and then to a map view so that the map view can make queries depending on what the user wants to see. I was consulting some apple sample code which looks like(from Recipes):

- (void)applicationDidFinishLaunching:(UIApplication *)application {
    recipeListController.managedObjectContext = self.managedObjectContext;
    [window addSubview:tabBarController.view];
    [window makeKeyAndVisible];
}

I know that is in the appDelegate, but I figure开发者_Python百科 that I can do the same when a row is selected or another view is pushed onto the stack, right? The problem is that I have configured most of my view with a nib which looks like so:

Due to this, I am unable to use a similar strategy that Apple employs to transfer a managedObjectModel to an alternate viewController(in this case PermitListViewController) because I don't access PermitListViewController directly when adding a subview. If anyone has any idea of how I would go about getting my managedObjectModel to my PermitListViewController. Please share! Thanks in advance!

EDIT: I am thinking of placing the managedObjectModel in a singleton class. What are your guys' thoughts on that? Good programming practice? Anything I should be aware of? Thanks.

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Why not have the NSManagedObjectContext on the app delegate? Then it would be easily accessible from all your view controllers, and as they are UI they execute on the main thread, and can therefore share the same MOC.

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I ended up creating a singleton class for the managedObjectModel using this as a reference (scroll down to "Creating a Singleton Instance").