Game Center deprecated methods in login()

***WORKS ONLY ON iOS 6 DEVICES ***

Fix new login method:

BOOL isViewOnScreen; //yes when login is on screen

• (void)login
  {
  GKLocalPlayer* localPlayer = [GKLocalPlayer localPlayer];
  if (localPlayer.isAuthenticated) {
  isViewOnScreen=NO;
  return;
  }

  NSLog(@"Game Center login ....");

  localPlayer.authenticateHandler =
  ^(UIViewController *viewController,
  NSError *error) {

  if (localPlayer.authenticated) {
     isAuthenticated = YES;
      [self retrieveScoresFromDevice];
      [self retrieveAchievementsFromDevice];
  } else if(viewController) {
      NSLog(@"Game Center shows login ....");
      isViewOnScreen=YES;
      [self presentViewController:viewController];
  } else {
       NSLog(@"Game Center error or canceled login ....");
      //User canceled Login view
     isAuthenticated = NO;
  isViewOnScreen=NO;
  }
  

  };
  }

pragma mark UIViewController stuff

-(UIViewController*) getRootViewController {
return [UIApplication
sharedApplication].keyWindow.rootViewController;
}

-(void)presentViewController:(UIViewController_)vc {
UIViewController_ rootVC = [self getRootViewController];
[rootVC presentViewController:vc animated:YES
completion:nil];
}