Question

I have a view based app (not navigation or tab based…)

My main view controller is called from the app delegate and initiated from a xib.

Then I use presentModalViewController to bring another view on the screen with it’s own xib and view controller.

I have no problems passing data to that view controller.

However, when I dismiss the second view controller, I want to send data back to the main view controller for my app, but I just can’t figure out how to reference it. Actually, I’d like to call a method in the main view controller if possible.

I’ve been struggling with this a bit and have found suggestions online but I just can’t seem to get it to work. I’m hoping someone can provide the sample code to do this.

P.s. is this “main view controller” still referred to as a “root view controller” or is that term only used when dealing with a view controller stack (i.e. navigation or tab view controller)

EDIT:
I’m sure Bryan’s solution would work so I have accepted as answer. However I ended up using NSNotificationCenter to get this to work and I find it a bit simpler to understand as a beginner

Answer 1

You can use the delegation pattern. In your modal view controller’s header file, create an interface for a new delegate protocol…

@protocol ModalViewControllerDelegate <NSObject>

- (void)sendData:(Data *)someData;

@end

…and give your ModalViewController a new instance variable that implements this protocol:

@property (nonatomic, assign) id<ModalViewControllerDelegate> delegate;

Your main view controller should implement this protocol…

@interface MainViewController : UIViewController <ModalViewControllerDelegate> {

…and set itself as the delegate before it presents the modal view controller:

ModalViewController *modalViewController = [[[ModalViewController alloc] init] autorelease];
[modalViewController setDelegate:self];
// Present modal view controller

The main view controller should implement the delegate protocol’s method:

- (void)sendData:(Data *)someData {
    NSLog("I have just received some data: %@", someData);
}

Then inside your modal view controller, you can simply call the following method whenever you want to send data back to the main view controller:

[delegate sendData:someData];