Access ViewController from AppDelegate

Question

My problem is the following,

In one of my ViewControllers, when the user taps a button , I register the device for notifications with this code.

[[UIApplication sharedApplication] registerForRemoteNotificationTypes: (UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound | UIRemoteNotificationTypeAlert)];

Then, in the AppDelegte, there are two methods. One that receives the token and one that gets the error.

- (void)application:(UIApplication*)application didRegisterForRemoteNotificationsWithDeviceToken:(NSData*)deviceToken - (void)application:(UIApplication*)application didFailToRegisterForRemoteNotificationsWithError:(NSError*)error

And now comes the problem, in didRegisterForRemoteNotificationsWithDeviceToken I need to send the token to my server, and with it some data that the user has entered in the View, like its username.

How can I get this data?

macserv · Accepted Answer · 2016-04-13 19:59:03Z

The NSNotificationCenter will serve you well here. In your AppDelegate's didRegisterForRemoteNotificationsWithDeviceToken, do this:

[[NSNotificationCenter defaultCenter] postNotificationName:@"RegistrationReceived" object:token];

And, in your controller's viewDidLoad,

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(updateRegistrationInfo:) name:@"RegistrationReceived" object:nil];

Be sure to implement -updateRegistrationInfo: (or whatever you want to name it) to receive the NSNotification and the token, which is passed in as the argument. Also, unregister for the notification when you no longer need it.

- (void)updateRegistrationInfo:(NSNotification *)notification { NSString *myObject = [notification object]; ... }

Mikhail Viceman · Accepted Answer · 2013-02-12 17:46:47Z

You can can add your ViewController as an instance variable to your AppDelegate class:

@interface AppDelegate : NSObject <UIApplicationDelegate> { @private // Instance variables UIWindow *mainWindow; // Main App Window UINavigationController *navigationController; UIViewController *someViewController; }

And then add some methods to someViewController that returns your requested data.

You can assign someViewController in - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions of the AppDelegate class in this way:

someViewController = [[UIViewController alloc] initWithNibName:nil bundle:nil]; navigationController = [[UINavigationController alloc] initWithRootViewController:someViewController];

ok, but now.. how do I assign the ViewController to this variable?
This will work, but it's kind of a hack... you're going backwards, looking up to the top of your hierarchy when what you want to do is propagate a notification forward, down to a controller. Check out NSNotificationCenter… I've provided some more detail in my answer to your question.

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