Why don't UISupportedInterfaceOrientations settings affect UIViewController behavior?

Question

Xcode (4) highlights the UISupportedInterfaceOrientations settings, but no matter how I set them, it does not appear to affect a basic app's functionality. The Xcode templates insert commented out implementation for programmatically reporting support in:

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Return YES for supported orientations.
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

In my experience, this code has nothing to do with the app's bundle settings. So, I wrote the following code to automatically report support for orientation based on the app settings.

Why isn't this the default implementation? Did I miss something and this code shouldn't be necessary? (Any improvements anyone can suggest?) I might turn this into a category for UIViewController

/**
 * This implementation coordinates the app's orientation support with the app
 * bundle settings, simplifying the configuration of the app's support for its
 * different orientations. 
 */
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    static NSString *_orientationFlagNames[] = {
        Nil,                                        // UIDeviceOrientationUnknown
        @"UIInterfaceOrientationPortrait",          // UIDeviceOrientationPortrait,
        @"UIInterfaceOrientationPortraitUpsideDown",// UIDeviceOrientationPortraitUpsideDown,
        @"UIInterfaceOrientationLandscapeRight",    // UIDeviceOrientationLandscapeLeft [sic]
        @"UIInterfaceOrientationLandscapeLeft"      // UIDeviceOrientationLandscapeRight [sic]
                                                    // UIDeviceOrientationFaceUp
                                                    // UIDeviceOrientationFaceDown
    };

    NSArray *supportedOrientation = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"UISupportedInterfaceOrientations"];

    BOOL shouldRotate = (interfaceOrientation < sizeof(_orientationFlagNames)/sizeof(NSString*)
        && [supportedOrientation containsObject:_orientationFlagNames[interfaceOrientation]]);
    return shouldRotate; 
}

Answer 1

I think there is a distinction here. The info.plist value indicates the orientations that the app supports whereas the shouldAutorotateToInterfaceOrientation: indicates the orientations a particular view is available in.

If you look here, it is clearly mentioned that the info.plist values help iOS choose the initial orientation to launch the application.