Is there a best practice for assigning UITabBarController-managed controller properties? - ios

Question

Say you've got a UIViewController subclass called BeverageViewController, and you are using four separate instances of this controller within a UITabBarController collection. You've also got a data structure of, say, four NSString string objects, #"Beer", #"Wine", #"Whiskey", and #"More Whiskey". Each string corresponds to one BeverageViewController instance, which will use the string for a text label within its view. Hence, when a particular BeverageViewController instance is executing its viewDidLoad method, it expects to have a public property assigned with with one of these four strings.
When one has such a controller as a segue destination within a UINavigationController hierarchy, one typically uses prepareForSegue:sender: to set a property of this destination controller before viewDidLoad is called.
I've been exploring how to set a controller property before viewDidLoad, when the controller is part of a UITabBarController collection. I've determined that implementing a UITabBarControllerDelegate's tabBarController:shouldSelectViewController: method is an ok approach, except you have to dick around to get the relevant tab index of the controller:
- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController {
NSInteger index = [tabBarController.viewControllers indexOfObject:viewController];
BeverageController *controller = (BeverageController *)viewController;
controller.beverageName = self.beverageNames[index];
return YES;
}
Don't be fooled: you can't use the tabBarController.selectedIndex; you can't use the delegate method tabBarController:didSelectViewController:, because this method fires after viewDidLoad. Furthermore, you can't use self.tabBarController.selectedIndex within the controller's implementation of viewDidLoad. These three approaches seem the most obvious, but they do not facilitate the goal above.
Oh lawd, lawd, if only tabBarController:didSelectViewController: fired before the controller's viewDidLoad method. But it doesn't. Nor does it precede viewWillAppear, and preparing the view within viewDidAppear is, well, moronic.
What's the best way to set a controller property within a UITabBarController collection that enables one to have access to the property within a viewDidLoad method, without resorting to abandoning IB and procedurally managing the UITabBarController? Is it my approach above? Is it to implement a custom UITabBarController and manipulate the controllers in its viewControllers property? Or did I miss the APIobvious?

Answer 1

If your setting everything up in IB and those strings for the BeverageController are constant, i.e. they don't change during runtime, you can set them up in IB directly.
In the IB's inspector there is an option called "User Defined Runtime Attributes". If your BeverageController subclass has a property called let's say controllerName, you just select that VC in IB and click the little plus sign under "User Defined Runtime Attributes", the attribute name would be controllerName, then select the string-type and input you value (f.e. "Beer").
If you need to change the values dynamically, your approach with tabBarController:shouldSelectViewController: is fine.

Answer 2

I use application:didFinishLaunchingWithOptions: to set up my viewControllers. Get the tabBarController from your window, and then get each viewController from the tabBarController.
Something like this:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
UITabBarController *tabBarController = (UITabBarController *)self.window.rootViewController;
NSAssert([tabBarController isKindOfClass:[UITabBarController class]], #"Must be a tabBarController");
MBFirstViewController *firstVC = tabBarController.viewControllers[0];
firstVC.foo = #"Bar";
MBSecondViewController *secondVC = tabBarController.viewControllers[1];
secondVC.foo = #"Baz";
return YES;
}