在开发中，我们可能会遇到类似这样的需求，在模态出的登录页面，再模态弹窗，直接进行弹窗是会出现警告的（无作用，）

Re:Warning: Attempt to present on

这时就需要我们拿到当前控制器的跟控制器来进行模态弹窗等操作。以下为获取当前显示的控制器的跟控制器方法

- (UIViewController*)topViewController

{

return[selftopViewControllerWithRootViewController:[UIApplicationsharedApplication].keyWindow.rootViewController];

}

- (UIViewController*)topViewControllerWithRootViewController:(UIViewController*)rootViewController

{

if([rootViewControllerisKindOfClass:[UITabBarControllerclass]]) {

UITabBarController*tabBarController = (UITabBarController*)rootViewController;

return[selftopViewControllerWithRootViewController:tabBarController.selectedViewController];

}elseif([rootViewControllerisKindOfClass:[UINavigationControllerclass]]) {

UINavigationController* navigationController = (UINavigationController*)rootViewController;

return[selftopViewControllerWithRootViewController:navigationController.visibleViewController];

}elseif(rootViewController.presentedViewController) {

UIViewController* presentedViewController = rootViewController.presentedViewController;

return[selftopViewControllerWithRootViewController:presentedViewController];

}else{

returnrootViewController;

}

}

这样就可以直接调用  [self topViewController];获取顶层控制器

[[self topViewController] presentViewController:[[UIViewController alloc] init] animated:YES completion:nil]; 如此就可以模态了