Objective c generics for something that isn't a collection type. Here is an example of producing a view controller from storyboard where you are returned the correct type thanks to generics.

objcGenerics

// Making a class since we can not add generics to UIStoryboard nor can we make a category for it.
@interface UIStoryboardHelper <__covariant T:UIViewController *> : UIStoryboard
- (T)vcFromIdentifier:(NSString *)identifier fromStoryboard:(UIStoryboard *)storyboard;
@end
@implementation UIStoryboardHelper
- (UIViewController *)vcFromIdentifier:(NSString *)identifier fromStoryboard:(UIStoryboard *)storyboard {
	return [storyboard instantiateViewControllerWithIdentifier:identifier];
}
@end

//usage
	GreenViewController *vc = [[UIStoryboardHelper <GreenViewController *> new] vcFromIdentifier:NSStringFromClass([GreenViewController class]) fromStoryboard:self.storyboard];
	[self presentViewController:vc animated:YES completion:nil];