Passing data back from a modal view in WatchKit

Question

When modally presenting, or pushing, an interface controller we can specify the context parameter to pass some data to the new controller as follows.

Answer 1

You can transfer back information via Protocols by passing self within the context:

InterfaceController.m

// don't forget to conform to the protocol!
@interface InterfaceController() 

//...

// in some method
[self pushControllerWithName:@"PictureSelectionController" 
                     context:@{@"delegate" : self}];

And setting the delegate like so:

PictureSelectionController.m

@property (nonatomic, unsafe_unretained) id delegate;

// ...

- (void)awakeWithContext:(id)context {
    [super awakeWithContext:context];

    // Configure interface objects here.
    if ([context isKindOfClass:[NSDictionary class]]) {
        self.delegate = [context objectForKey:@"delegate"];
    }
}

Don't forget to declare your protocol:

PictureSelectionController.h

@protocol PictureSelectionControllerDelegate 

- (void)selectedPicture:(UIImage *)picture;

@end

Then you can call that method from PictureSelectionController.m:

- (IBAction)buttonTapped {
    // get image
    UIImage *someCrazyKatPicture = //...
    [self.delegate seletedPicture:someCrazyKatPicture];
}

And receive it in the delegate method within InterfaceController.m:

- (void)selectedPicture:(UIImage *)picture {
    NSLog(@"Got me a cat picture! %@", picture);
}