Question

I have a question regarding how to pass around NSManagedObjectContext. In my app, it seems like it’s my AppDelegate that handles NSManagedObjectContext, so I shouldn’t create other NSManagedObjectContexts in my other ViewControllers.

So the question is…

There is any convention or smart method to do this?

Thanks.

Answer 1

The way I pass the NSManagedObjectContext is to simply have an iVar in each view controller you pass it to. I usually modify the initialiser to include assignment, something like this….

MyNewViewController.h

 @interface MyNewViewController : UIViewController {
     NSManagedObjectContext *managedObjectContext;
 }
 ...

MyNewViewController.m

@implementation MyNewViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil andContext:(NSManagedObjectContext *)ctx {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        managedObjectContext = ctx;
    }
    return self;
}

....       

Then when you call the view controller, you simply use the modified initialiser. Like…

MyNewViewController *nv = [[MyNewViewController alloc] initWithNibName:@"MyNewViewController" bundle:nil andContext:self.managedObjectContext];

Now you’ve got a reference to the managedObjectContext which you can use within your view controller.