How to enumerate view controllers on iPhone?

I have a modal view controller which fetches a password. Since I don't want the password written to disk if my application is interrupted, I want to cear the password on applicationWillResignActive. (For those who may comment, I know the secure text field does not properly zeroize).

I've tried the following code, and my view controller is never located. For the first set of code (UIView) I believe its because I'm mixing and matching views and view controllers. I'm not sure why the second set of code (UIViewC开发者_如何学编程ontroller) is not working since a few folks have suggested it.

How does one enumerate view controllers and locate a controller of interest? I simply want to send clearPassworAndPin to PasswordPromptController if present (since viewWillDisappear is not always sent when the view disappears).

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Modified 7KV7 and Jhaliya answer is below (it worked). The 'if' statement using viewController.modalViewController was executed 5 times (once for each controller in the tab view). So the single modal controller of interest was sent the clearPasswords message 5 times.

for (UIViewController * viewController in viewsControllers)
{
    if ([viewController isKindOfClass:passwordPromptClass])
    {
        [(PasswordPromptController *)viewController clearPassworAndPin];
    }
    else
    {
        if(viewController.modalViewController)
            [self clearPasswords:[NSArray arrayWithObjects:viewController.modalViewController, nil]];
    }
}

Using UIViews (no joy)

- (void)applicationWillResignActive:(UIApplication *)application
{
  if(application.windows != nil)
    [self clearPasswords:application.windows];
}

- (void)clearPasswords:(NSArray *)subviews
{
  Class passwordPromptClass = [PasswordPromptController class];

  for (UIView * subview in subviews)
  {
    if ([subview isKindOfClass:passwordPromptClass])
      [(PasswordPromptController *)subview clearPassworAndPin];
  }
}

Using UIViewController (no joy)

- (void)applicationWillResignActive:(UIApplication *)application
{
  if(tabBarController.viewControllers != nil)
    [self clearPasswords:tabBarController.viewControllers];
}

- (void)clearPasswords:(NSArray *)viewsControllers
{
  Class passwordPromptClass = [PasswordPromptController class];

  for (UIViewController * viewController in viewsControllers)
  {
    if ([viewController isKindOfClass:passwordPromptClass])
      [(PasswordPromptController *)viewController clearPassworAndPin];
  }
}

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NSArray *array = [self.navigationController viewControllers];
yourViewController = [array objectAtIndex:yourChoiceOfIndex];

Hope it helps.

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At the point where you present the PasswordPromptController as a modalViewController could you not store it as an instance variable? Then, in your applicationWillResignActive: callback you will have a handle to the VC to message against.

Be sure to release and nullify your reference to the PasswordPromptController reference when it gets dismissed.

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you will have to go through the navigation stack to get the controllers.

Use UINavgationController below method to get all viewController in your navigation stack.

@property(nonatomic, copy) NSArray *viewControllers

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hmm..., I have to say I like to give alternative suggestions/solutions as many folks have tried to answer you question specifically.

If you found it's not easy to find the PasswordPromptController by enumerating view controllers, you can just declare (alloc/init) that controller in your app delegate, whenever you need to use it in other controllers, get it through app delegate, do something like presenting as a modal view. When you want to do something against it in your app delegate, e.g. clear the pwd, it's super easy because you have the reference to it.