How to get a call event using CTCallCenter:setCallEventHandler: that occurred while the app was suspended?

Question

The documentation for CTCallCenter:setCallEventHandler: states that:

However, call events can also take place while your application is suspended.

Answer 1

I've found a solution but I have no idea why it's working. Only thing I can think of is a bug in GCD and/or CoreTelephony.

Basically, I allocate two instances of CTCallCenter like this

void (^block)(CTCall*) = ^(CTCall* call) { NSLog(@"%@", call.callState); };

-(BOOL)application:(UIApplication*)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions
{
    callCenter1 = [[CTCallCenter alloc] init];
    callCenter1.callEventHandler = block;

    callCenter2 = [[CTCallCenter alloc] init];
    callCenter2.callEventHandler = block;

    return YES;
}

Similar Code in Swift:

func block (call:CTCall!) {
        println(call.callState)
    }

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        //Declare callcenter in the class like 'var callcenter = CTCallCenter()'
        callcenter.callEventHandler = block

        return true
    }

To test this I made a call, answered it and then hanged up it while app was in background. When I launched it I received 3 call events: incoming, connected, disconnected.