ios - 在 ViewController 之外显示 UIAlertController

Question

我无法显示我的 UIAlertController，因为我试图在一个不是 ViewController 的类中显示它。

我已经尝试添加它了:

 var alertController = UIAlertController(title: "Title", message: "Message", preferredStyle: .Alert)

UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(alertController, animated: true, completion: nil)

哪个不工作...我还没有找到适合我的解决方案。

Answer 1

我在 UIAlertController 上写了这个 extension 来带回 show()。
它使用递归来查找当前的顶 View Controller :

extension UIAlertController {
    
    func show() {
        present(animated: true, completion: nil)
    }
    
    func present(animated: Bool, completion: (() -> Void)?) {
        if let rootVC = UIApplication.shared.keyWindow?.rootViewController {
            presentFromController(controller: rootVC, animated: animated, completion: completion)
        }
    }
    
    private func presentFromController(controller: UIViewController, animated: Bool, completion: (() -> Void)?) {
        if 
            let navVC = controller as? UINavigationController,
            let visibleVC = navVC.visibleViewController
        {
            presentFromController(controller: visibleVC, animated: animated, completion: completion)
        } else if
            let tabVC = controller as? UITabBarController,
            let selectedVC = tabVC.selectedViewController
        {
            presentFromController(controller: selectedVC, animated: animated, completion: completion)
        } else if let presented = controller.presentedViewController {
            presentFromController(controller: presented, animated: animated, completion: completion)
        } else {
            controller.present(self, animated: animated, completion: completion);    
        }
    }
}

现在很简单:

var alertController = UIAlertController(title: "Title", message: "Message", preferredStyle: .Alert)
alertController.show()