Watchkit -application: handleWatchKitExtensionRequest error

Question

I'm getting the following error when requesting a dictionary of XML items via the above method:

> NSLocalizedDescription=The UIApplicationDelegate in the iPhone App never called reply() in -[UIApplicationDelegate application:handleWatchKitExtensionRequest:reply:]

I have no problem passing an NSDictionary consisting of an NSMutableArray of NSStrings.

From the interface controller:

- (void) requestFeedsFromPhone
{
    [WKInterfaceController openParentApplication:@{@"request":@"feeds"}
                                       reply:^(NSDictionary *replyInfo, NSError *error) {

                                           // the request was successful
                                           if(error == nil) {

                                               // get the array of items
                                               NSMutableDictionary *tempDictionary = replyInfo[@"feeds"];


                                               NSLog(@"tempDictionary: %@", tempDictionary[@"feedsArray"]);
                                               self.feeds = tempDictionary[@"feedsArray"];
                                               [self setupTable];
                                           }
                                           else{
                                               NSLog(@"ERROR: %@", error);
                                           }
                                       }];
}

In the app delegate:

- (void) application:(UIApplication *)application
handleWatchKitExtensionRequest:(NSDictionary *)userInfo
           reply:(void (^)(NSDictionary *))reply
{

    MasterViewController *mainController = (MasterViewController*)  self.window.rootViewController;

    //this is the troublesome line - calling this method results in the error
    NSDictionary *feedsDictionary = [mainController returnFeedsDictionary];

    reply(@{@"feeds": feedsDictionary});
}

In the MasterViewController:

-(NSDictionary *) returnFeedsDictionary
{

    NSURL *url = [NSURL URLWithString:@"http://www.nasa.gov/rss/dyn/lg_image_of_the_day.rss"];
    SeparateParser *separateParser = [[SeparateParser alloc] initWithURL:url];
    [separateParser parse];
    NSArray *tempArray = [separateParser returnFeeds];
    return @{@"feedsArray": tempArray};

}

The returnFeeds method returns an NSMutableArray of NSMutableDictionarys filled with NSMutableStrings (title, link, imageURL, etc).

I'm assuming my problem is that some of my data isn't property list compliant but I thought arrays, strings, and dictionaries were acceptable.

Answer 1

You are hitting the Law of Leaky Abstractions.

Your iPhone-App and WatchKit-Extension run as two separate processes and two separate sandboxes. The OpenParentApplication/handleWatchKitExtensionRequest/reply mechanism is but a convenience mechanism that Apple provides to wrap intra-process-communication.

The Abstraction Leak:

reply(feedsDictionary)

The returned dictionary can only contain

• NSData
• NSString
• NSDate
• NSArray

• NSDictionary

  If your return dictionary contains anything beyond that, like a custom class instance, then you get that crappy error saying reply() was never called, even though you did!

---

---

Solution 1: Serialize your object and send it from app-to-Watch, and then de-serialize on watch (aka Marshalling/Unmarshalling).

• This requires using NSCoding, as mentioned in an above post: Serialize to NSData* stream, send reply(dataStream) and then de-serialize in the WatchKit Extension.
• NSCoding is a pain. You need to use NSKeyedArchiver explicitly to serialize before sending, and NSKeyedUnarchiver to de-serialize tutorial here.
• Requires a lot of cruft code to support encode/Decode within the class Object itself (to satisfy NSCoder)

Solution 2: Simply pass a string to act as Key, and instantiate your object inside of the Watch Extension (instead of passing the fat object instance itself)

• Allow WatchKit Extension to compile against your class files, via clicking on the {class}.m, pressing command+option+1, and clicking the "...WatchKit Extension" checkbox under Target Membership (you need to do this anyway, even with solution 1)

• e.g. Your WatchKit Extension would alloc/init a new instance of the model, rather than trying to pass that across

• e.g. You would Pass the URL, as a string, and the WatchKit extension would make NSURLConnection call.

Answer 2

In handleWatchKitExtensionRequest, make sure that you start a background task as specified in the documentation. This ensures that the main app on the iPhone is not suspended before it can send its reply.

Code in the app delegate of the main app on iPhone:

- (void)application:(UIApplication *)application handleWatchKitExtensionRequest:(NSDictionary *)userInfo reply:(void ( ^)( NSDictionary * ))reply
{
   __block UIBackgroundTaskIdentifier watchKitHandler;
   watchKitHandler = [[UIApplication sharedApplication] beginBackgroundTaskWithName:@"backgroundTask"
                                                               expirationHandler:^{
                                                                 watchKitHandler = UIBackgroundTaskInvalid;
                                                               }];

   if ( [[userInfo objectForKey:@"request"] isEqualToString:@"getData"] )
   {
      // get data
      // ...
      reply( data );
   }

   dispatch_after( dispatch_time( DISPATCH_TIME_NOW, (int64_t)NSEC_PER_SEC * 1 ), dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0 ), ^{
       [[UIApplication sharedApplication] endBackgroundTask:watchKitHandler];
    } );
}

Answer 3

You may want to try using NSKeyedArchiver on your reply dictionary. I had this issue because of serialization issues with the data and this helped.