didReceiveApplicationContext not being called

Question

I have just set up WCConnectivity in my app using tutorials/sample code and I feel I have it implemented correctly. I am not using the simulator to test. For some reason, the didReceiveApplicationContext is not being called in the watch app, even though everything is set up correctly.

I've tried calling in the the Interface Controller of the WatchKit app, in the ExtensionDelegate and using NSUserDefaults to set the Interface Controller data instead.

iOS App

ViewController.m

- (void) viewDidLoad{
if ([WCSession isSupported]) {
    WCSession *session = [WCSession defaultSession];
    session.delegate = self;
    [session activateSession];
  }
}

-(void) saveTrip{
NSMutableArray *currentTrips = [NSMutableArray arrayWithArray:[self.sharedDefaults objectForKey:@"UserLocations"]];

NSData *data = [NSKeyedArchiver archivedDataWithRootObject:newLocation];
[currentTrips addObject:data];
[self.sharedDefaults setObject:currentTrips forKey:@"UserLocations"];
[self.sharedDefaults synchronize];

WCSession *session = [WCSession defaultSession];
NSDictionary *applicationDict = [[NSDictionary alloc] initWithObjects:@[currentTrips] forKeys:@[@"UserLocations"]];;
[session updateApplicationContext:applicationDict error:nil];
}

Watch Extension Code

ExtensionDelegate.m

- (void)applicationDidFinishLaunching {
if ([WCSession isSupported]) {
    WCSession *session = [WCSession defaultSession];
    session.delegate = self;
    [session activateSession];
}
}
- (void)session:(nonnull WCSession *)session didReceiveApplicationContext:(nonnull NSDictionary<NSString *,id> *)applicationContext {
self.places= [applicationContext objectForKey:@"UserLocations"];
[[NSUserDefaults standardUserDefaults] setObject:self.places forKey:@"UserLocations"];
[[NSUserDefaults standardUserDefaults] synchronize]; 
}

InterfaceController.m

- (void)willActivate {
[super willActivate];
self.placesData = [NSMutableArray arrayWithArray:[[NSUserDefaults standardUserDefaults] objectForKey:@"UserLocations"]];
[self loadData];
}

Answer 1

For me it was two things:

1. Passing invalid values in the dictionary. Can't even pass NSNull() to represent nil values. If you have data in there that can't be represented in a plist, it fails.

2. If the dictionary doesn't change, subsequent calls to updateApplicationContext won't trigger a corresponding call to didReceiveApplicationContext. To force an update—perhaps in debug builds—you could add a UUID to the payload, e.g.

   context["force_send"] = UUID().uuidString

Answer 2

It might prove useful to handle any errors, so change:

[session updateApplicationContext:applicationDict error:nil];

to

NSError *error;    
if (![session updateApplicationContext:applicationDict error:&error]) {
    NSLog(@"updateApplicationContext failed with error %@", error);
}