Question

I have standard view controller acting as the delegate for a modal view controller over it.
This modal view controller is contained in a navigation controller.

After presenting the modal, and pushing another view controller onto the navigation stack, I want to pass some data back to the initial delegate view controller (that presented the modal).

Should I pass the message back up the navigation stack to the root view controller of the modal navigation controller first, and just use the delegate methods of that controller?

OR

Should I just pass the delegate property along to the nested view controller and then call the delegate directly with a separate protocol implemented. It work doing this, but I have to use

@property (nonatomic, weak) id delegate;

instead of

@property (nonatomic, weak) id <NestedViewDelegate> delegate;

otherwise I get an incompatible type error when I pass the delegate from the preview view controller in the stack:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

{

NestedViewController *nest = [[NestedViewController alloc] init];

// @property id <RootViewControllerDelegate> delegate
[nest setDelegate:[self delegate]];

[[self navigationController] pushViewController:nest animated:YES];

}

What is the best practice for this kind of scenario?

Thanks

Answer 1

I would consider using notifications to decouple this. Checkout NSNoticiationCenter.

You register for a notification in your root and publish in you child.

http://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/nsnotificationcenter_Class/Reference/Reference.html

EXAMPLE

In your Child object you do something like this:

[[NSNotificationCenter defaultCenter] postNotificationName:kMyNotificationName object:self userInfo:@{ @"key" : @"value" }]];

kMyNotificationName is defined in a shared place, like the pch or a Constants.h.

In the Root you would do something like this, either in init or perhaps whenever you push the child.

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(myNotificationName:) name:kMyNotificationName object:nil];

Don’t forget to remove observers in your dealloc or when you pop the child.

[[NSNotificationCenter defaultCenter] removeObserver:self kMyNotificationName object:nil];

Now you can handle the notification something like this:

- (void)myNotificationName:(NSNotification *)note
{
     NSDictionary *userInfo = [note userInfo];

     // Do stuff using the information passed in.
}