Never initialize multiple UICollectionViewControllers with the same UICollectionViewLayout instance

NeverCreateTabsLikeThis.mm

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

//	this subclass defines itemsSize as {320, 88}
	MyUICollectionViewFlowLayout *l = [[MyUICollectionViewFlowLayout alloc] init];

	//	initialize one subclass of UICollectionViewController
	MainViewController *mvc = [[MainViewController alloc] initWithCollectionViewLayout:l];

	//	initialize another with same layout
	//	but inside this init method do: 
	//	l.itemSize = CGSizeMake(320,44)
	SecondViewController *novc = [[SecondViewController alloc] initWithCollectionViewLayout:l];

	//	that change 44 is also applied to MainViewController layout
	
	self.tabBarController = [[UITabBarController alloc] init];
	self.tabBarController.viewControllers = @[mvc, novc];
	self.window.rootViewController = self.tabBarController;


	//	in hindsight, this was really stupid thing to do, but it's an easy copy/paste error to do.
	//	grumpf.
}