How to access View Controller from Tab bar controller?

I have a tab bar controller and each tab consist of a navigation controller.

How can I access a specific view controller in a navigation controller in a tab so that I can access a property specific to the view controller?

I tried the following code:

//Get the navigation controller of the 3rd tab
self.tabController.selectedViewController 
= [self.tabController.viewControllers objectAtIndex:2];

//Attempt to retrieve the viewcontroller I want from the tabcontroller
SomeViewController *svc = (SomeViewController *)self.tabController.selectedViewController;

//Attempting to access a BOOLEAN property in svc viewcontroller
svc.someProperty = YES;

The above code failed because it seems that "self.tabController.sel开发者_Go百科ectedViewController" returns me a navigation controller. How can I extend the code so that I can access "svc.someProperty"?

You can use -topViewController to get the view controller from the navigation controller (or -visibleViewController if you are using modal view controllers).

If self.tabController.selectedViewController is your navigation view controller, then you can access the currently visible controller using:

visibleViewController

and the top view controller using:

topViewController

If this does not allow you to get to SomeViewController, you can iterate through the list of controllers pushed on the navigation controller stack:

viewControllers

Since the view controller is a subview of the returned UINavigationController(SVC), you could just send it the following method [svc topViewController];. That should return you the view controller and then you should be able to access the property.