Pass message to Apple Watch using MMWormhole - ios

Question

I'm developing an Apple Watch App, and I need to notify the watch when certain changes occur in the parent application. I'm using the MMWormhole library found on GitHub, but I'm having trouble passing messages from the phone to the watch. Here is my code, do you have any ideas on why this is happening?
My main viewController code looks like this
ViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
self.wormhole = [[MMWormhole alloc] initWithApplicationGroupIdentifier:#"com.mycompany.myapp"
optionalDirectory:#"wormhole"];
NSString *myString = [[NSString alloc] initWithFormat:#"Test String"];
[self.wormhole passMessageObject:#{#"string" : myString}
identifier:#"messageIdentifier"];
My InterfaceController from my WatchkitExtension looks like this:
InterfaceController.m
- (void)awakeWithContext:(id)context {
[super awakeWithContext:context];
// Initialize the wormhole
self.wormhole = [[MMWormhole alloc] initWithApplicationGroupIdentifier:#"com.mycompany.myapp"
optionalDirectory:#"wormhole"];
// Obtain an initial value for the selection message from the wormhole
id messageObject = [self.wormhole messageWithIdentifier:#"messageIdentifier"];
NSString *string = [messageObject valueForKey:#"string"];
if (string != nil) {
NSLog(string);
[myLabel setText:string];
}
// Listen for changes to the selection message. The selection message contains a string value
// identified by the selectionString key. Note that the type of the key is included in the
// name of the key.
[self.wormhole listenForMessageWithIdentifier:#"messageIdentifier" listener:^(id messageObject) {
NSString *string = [messageObject valueForKey:#"string"];
if (string != nil) {
[self.myLabel setText:string];
}
}];
}
Thank you!

Answer 1

Is "com.mycompany.myapp" the real value you use in the app? Because group identifiers have to start with group..
If you use a wrong group identifier everything fails because the containerURLForSecurityApplicationGroupIdentifier call inside MMWormhole returns nil. Unfortunately the developers of MMWormhole didn't do any checks or asserts to make sure that the shared group identifier is correct.
So I would recommend to stop concentrating on MMWormhole for a minute. Instead add this code early in your code (e.g. applicationDidFinishLaunching) to verify that your container identifier is correct:
NSFileManager *fileManager = [[NSFileManager alloc] init];
NSURL *appGroupContainer = [fileManager containerURLForSecurityApplicationGroupIdentifier:#"group.com.mycompany.myapp"];
if (!appGroupContainer) {
NSLog(#"group identifier incorrect, or app groups not setup correctly");
}
This will tell you if your app group setup is incorrect.
I'm not sure how far you are into setting up app groups, but you have to use the group identifier you used in the App Groups capabilities section of your project.