iosuinavigationcontrollerinstancetype

Confusion about initWithNavigationBarClass - how to use (new instanceType method)


This works great:

UINavigationController *nc =
    [[UINavigationController alloc]
    initWithNavigationBarClass:[GTScrollNavigationBar class]
    toolbarClass:[UIToolbar class]];
nc.viewControllers = @[firstPage];
self.window.rootViewController = nc;

but this does not work:

UINavigationController *nc =
    [[UINavigationController alloc]
    initWithNavigationBarClass:[GTScrollNavigationBar class]
    toolbarClass:[UIToolbar class]];
self.window.rootViewController = nc;
self.window.rootViewController.viewControllers = @[firstPage]; // ERROR

how can it be? Thanks


Solution

  • self.window.rootViewController.viewControllers = @[firstPage];
    

    does not compile because the rootViewController property of UIWindow is declared as a (generic) UIViewController (which does not have a viewControllers property), and not as a UINavigationController.

    The compiler does not "know" that the root view controller is actually a navigation controller in your case.

    So either you proceed as in your first code block, or you have to add an explicit cast:

    ((UINavigationController *)self.window.rootViewController).viewControllers = @[firstPage];