Question

我是swift3的新手。现在，我正在寻找一种从其他swift.file

调用alert函数的方法

像这样：

//MainView.swift
//Call function
AlertFun.ShowAlert(title: "Title", message: "message..." )

//Another page for storing functions
//Function.swift

public class AlertFun {
    class func ShowAlert(title: String, message: String ) {    
        let alert = UIAlertController(title: tile, message: message, preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: nil))
        self.present(alert, animated: true, completion: nil)
    }
}

这里的问题......不能这样做......

    self.present(alert, animated: true, completion: nil)

我该如何实施？感谢。

Answer 1

将viewController引用作为参数传递给showAlert函数，如：

//MainView.swift
//Call function
AlertFun.ShowAlert(title: "Title", message: "message...", in: self)

//Another page for storing functions
//Function.swift

public class AlertFun {
    class func ShowAlert(title: String, message: String, in vc: UIViewController) {    
        let alert = UIAlertController(title: tile, message: message, preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: nil))
        vc.present(alert, animated: true, completion: nil)
    }
}

Answer 2

您的控制器的调用方法

Utility.showAlertOnViewController(targetVC: self, title: "", message:"")

您的班级

class Utility: NSObject {
    class func showAlertOnViewController(
            targetVC: UIViewController,
            title: String,
                message: String)
        {

            let alert = UIAlertController(
                title: title,
                message: message,
                preferredStyle: UIAlertControllerStyle.alert)
            let okButton = UIAlertAction(
                title:"OK",
                style: UIAlertActionStyle.default,
                handler:
                {
                    (alert: UIAlertAction!)  in
            })
            alert.addAction(okButton)
            targetVC.present(alert, animated: true, completion: nil)
        }
}

Answer 3

我发现我看到的所有示例都不会在没有警告的情况下起作用：

尝试在视图不在窗口层次结构中的<UIAlertController: 0x7f82d8825400>上显示<app name>！

对我有用的代码如下。函数调用与以前一样：

 AlertFun.ShowAlert(title: "Title", message: "message...", in: self)

但是，要使其正常工作，Function.swift文件必须在DispatchQueue.main.async内部显示警报。因此Function.swift文件应如下所示：

public class AlertFun
{
    class func ShowAlert(title: String, message: String, in vc: UIViewController)
    {
        DispatchQueue.main.async
            {
                let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertController.Style.alert)
                alert.addAction(UIAlertAction(title: "Ok", style: UIAlertAction.Style.default, handler: nil))
                vc.present(alert, animated: true, completion: nil)
        }
    }
}

来自其他swift.file的swift3调用alert函数

3 个答案: