Question

I created a new window-based project and couldn’t figure out why it wasn’t doing anything. Eventually I put an NSLog right after didFinishLaunching and it’s never logged when I run it. Here is all of the code I have written:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    NSLog(@"didFinishLaunching");

    // Get the device object and turn proximity monitoring on
    UIDevice *d = [UIDevice currentDevice];
    [d setProximityMonitoringEnabled:YES];

    // Get the NSNotificationCenter object
    NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];

    // Sign up to receive notifications when the proximity state changes
    [nc addObserver:self selector:@selector(proximityChanged:) name:UIDeviceProximityStateDidChangeNotification object:d];
    NSLog(@"Observing...");

    [self.window makeKeyAndVisible];
    return YES;

}

- (void)proximityChanged:(NSNotification *)note {

    // Print out the changes of proximity state
    NSLog(@"Proximity Changed: %d", [[note object] proximityState]);

}

That’s the entirety of what I’ve written and nothing is logged when I run it on the simulator or on my device. Any thoughts?

Answer 1

Well, you are talking about Application Delegate. The obvious reason – your object is not set as an application delegate.

Looking at Apple documentation there is quite a few ways to accomplish it:

1. Remove application delegate binding in Interface Builder (.xib file for the window)
2. Set 4th parameter of UIApplicationMain in main.h to something else than nil.

Check you nib file in Interface Builder and see if the App Delegate is setup.

Reference to documentation
Core Application Design

The application delegate is a custom object that you provide at
application launch time, usually by embedding it in your application’s
main nib file. The primary job of this object is to initialize the
application and present its window onscreen. The UIApplication object
also notifies this object when specific application-level events
occur, such as when the application needs to be interrupted (because
of an incoming message) or moved to the background (because the user
tapped the Home button).

---

The fourth parameter identifies the class of the application delegate.
The application delegate is responsible for managing the high-level
interactions between the system and your custom code. Specifying nil
tells UIKit that the application delegate object is located in the
application’s main nib file (which is the case for applications built
using the Xcode templates).