How to check if a specific UIViewController's view is currently visible? [duplicate]

After doing some research, I found this answer in a different question posted on here...This seems to be the best way...

The view's window property is non-nil if a view is currently visible, so check the main view in the view controller:

if (viewController.isViewLoaded && viewController.view.window){
    // viewController is visible
}

Add this to your controllers, or to a subclass of UIViewController that you can then subclass further. Access it using a property or the variable:

- (void)viewDidAppear:(BOOL)animated
{
 [super viewDidAppear:animated];
 visible = YES;
}

- (void)viewWillDisappear:(BOOL)animated
{
 visible = NO;
 [super viewWillDisappear:animated];
}