如何在Swift中显示来自另一个班级的警报? [英] How to show an alert from another class in Swift?

问题描述

我有一个主类AddFriendsController，它运行以下代码行:

I have a main class, AddFriendsController, that runs the following line of code:

ErrorReporting.showMessage("Error", msg: "Could not add student to storage.")

然后我有了这个ErrorReporting.swift文件:

导入基金会

class ErrorReporting {
    func showMessage(title: String, msg: String) {
        let alert = UIAlertController(title: title, message: msg, preferredStyle: UIAlertControllerStyle.Alert)
        alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
        self.presentViewController(alert, animated: true, completion: nil)
    }
}

很显然，self在这里不起作用，给我一个错误.我希望在许多不同的swift文件中使用相同的方法，如何引用当前打开的视图控制器(在这种情况下为AddFriendsController)?

Obviously, self wouldn't work here, and is giving me an error. How can I refer to the currently open view controller (i.e. AddFriendsController in this circumstance), as I am wishing to use this same method in many different swift files?

谢谢.

推荐答案

您可以为UIApplication创建扩展方法(例如)，该方法将返回topViewController:

You can create extension method for UIApplication (for example) which will return your topViewController:

extension UIApplication {

    static func topViewController(base: UIViewController? = UIApplication.sharedApplication().delegate?.window??.rootViewController) -> UIViewController? {
        if let nav = base as? UINavigationController {
            return topViewController(nav.visibleViewController)
        }
        if let tab = base as? UITabBarController, selected = tab.selectedViewController {
            return topViewController(selected)
        }
        if let presented = base?.presentedViewController {
            return topViewController(presented)
        }

        return base
    }
}

然后您的课程将如下所示:

And then your class will look like this:

class ErrorReporting {

    static func showMessage(title: String, msg: String) {
        let alert = UIAlertController(title: title, message: msg, preferredStyle: UIAlertControllerStyle.Alert)
        alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
        UIApplication.topViewController()?.presentViewController(alert, animated: true, completion: nil)
    }
}

方法必须为static才能将其称为ErrorReporting.showMessage.

Method need to be static to be able to call it as ErrorReporting.showMessage.

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