Ios UIAlertView仅显示一次

我有一个只需弹出一次的条款协议，但是每次应用程序启动时它都会弹出，我如何才能使它只弹出一次，当按下时，我同意不再弹出，除非应用程序被删除并重新下载。我正在努力跟上

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我的agree函数是一个警报控制器

我忘记在agree（）之后添加

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如果同意或不同意，只需在UserDefaults中保存一个bool和答案，并检查键“演练”是否存在。如果没有，您将向他显示警报，如果发现，则什么也不做

将其添加到

viewdideappear

方法中的初始viewController：

    let alert = UIAlertController(title: "Message", message: "You need to agree to terms and conditions", preferredStyle: .alert)
    let action = UIAlertAction(title: "Not Agreed", style: .default) { (action) in

        UserDefaults.standard.set(false, forKey: "WalkThrough")

        alert.dismiss(animated: true, completion: nil)
    }
    let action2 = UIAlertAction(title: "Agreed", style: .default) { (action) in

        UserDefaults.standard.set(true, forKey: "WalkThrough")

        alert.dismiss(animated: true, completion: nil)
    }

    alert.addAction(action)
    alert.addAction(action2)


    if (UserDefaults.standard.object(forKey: "WalkThrough") == nil) {
        //show alert and save answer
        self.present(alert, animated: true, completion: nil)

    }

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请使用问题的编辑链接添加其他信息。回答后按钮只能用于完整回答问题。-编辑什么？完整的答案是，我忘记添加行以将其设置为true，这就是答案

UserDefaults.standard.set(true, forKey: "Walkthrough")

    let alert = UIAlertController(title: "Message", message: "You need to agree to terms and conditions", preferredStyle: .alert)
    let action = UIAlertAction(title: "Not Agreed", style: .default) { (action) in

        UserDefaults.standard.set(false, forKey: "WalkThrough")

        alert.dismiss(animated: true, completion: nil)
    }
    let action2 = UIAlertAction(title: "Agreed", style: .default) { (action) in

        UserDefaults.standard.set(true, forKey: "WalkThrough")

        alert.dismiss(animated: true, completion: nil)
    }

    alert.addAction(action)
    alert.addAction(action2)


    if (UserDefaults.standard.object(forKey: "WalkThrough") == nil) {
        //show alert and save answer
        self.present(alert, animated: true, completion: nil)

    }