Passing an image from iPhone to Apple Watch not working

Question

Most tutorials on passing an image talk about existing images. I am attempting to generate images at runtime on the iPhone and pass to the Apple Watch.

I was using MMWormhole as referenced from SO Question but that didn't get my images through.

I've now tried using + openParentApplication on WKInterfaceController directly. I get an error:

Property list invalid for format: 200 (property lists cannot contain NULL)

I look this up and see UIImage cannot be serialized. So now I try to convert UIImage > NSData > NSString and send

- (void)awakeWithContext:(id)context {
    [super awakeWithContext:context];
    self.timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(loop) userInfo:nil repeats:true];
};


- (void)loop {
    [WKInterfaceController openParentApplication:nil reply:^(NSDictionary *replyInfo, NSError *error) {
        NSData *m = replyInfo[@"image"];
        UIImage *img = [UIImage imageWithData:m];
        [self.image setImage:img];
    }];
//    [self.wormhole passMessageObject:@"hello" identifier:@"hello"];
}



AppDelegate
    - (void)application:(UIApplication *)application handleWatchKitExtensionRequest:(NSDictionary *)userInfo reply:(void (^)(NSDictionary *))reply {
        UIImage *image = [UIImage imageNamed:@"cat.png"];
        NSData *data = UIImagePNGRepresentation(image);
        NSDictionary *d = @{@"image" : data};
        reply(d);
    }

Answer 1

You need to specify app group id on both ends. Like:

MMWormhole *wormhole = [[MMWormhole alloc] initWithApplicationGroupIdentifier:appGroupId optionalDirectory:kWormholeDirectory];