Swift 4：使用日历检查自首次启动以来是否已过去一周、一个月、两个月等

Question

我正在尝试添加计时器，以便在应用程序初始启动日期后的一周、一个月、两个月等时间出现一个按钮。

我已经使用了 Date.addingTimeInterval（见下面的代码），但它似乎在更长的时间段内效果不佳 (week/months)。 Swift 文档建议使用日历，但我不确定该怎么做。

override func viewDidLoad() {
       super.viewDidLoad()

        if installedDate == nil {
            installedDate = Date()
            let timer = Calendar.current

            Button1.isHidden = true
            Button2.isHidden = true
            Button3.isHidden = true
        }

        else {
            print("Not first run")
            print(installedDate!)

            let Button1Date = Date().addingTimeInterval(604800)      //for after 1 week
            let Button2Date = Date().addingTimeInterval(2592000)     //for after 1 month
            let Button3Date = Date().addingTimeInterval(5184000)     //for after 2 months


            if installedDate == Button1Date {
                Button1.isHidden = false
            }
            if installedDate == Button2Date {
                Button2.isHidden = false
            }
            if installedDate == Button3Date {
                Button.isHidden = false
            }

        }

    }

    var installedDate: Date? {
        get {
            return UserDefaults.standard.object(forKey: "installedDateKey") as? Date
        }
        set {
            UserDefaults.standard.set(newValue, forKey: "installedDateKey")
        }
    }

将发布日期与我需要的预期日期进行比较的更有效方法是什么？

Answer 1

根据我对您问题的了解，如果他们使用该应用程序超过一定时间，您希望显示一个按钮。如果是这样的话，我写了一些对你有帮助的代码：

let timeSinceInstalled = -(installedDate ?? Date()).timeIntervalSinceNow

Button1.isHidden = timeSinceInstalled < 604800
Button2.isHidden = timeSinceInstalled < 2592000
Button3.isHidden = timeSinceInstalled < 5184000

您实际上可以替换 viewDidLoad() 函数中的大部分代码，甚至是检查 installedDate == nil 的部分。这是您的更新代码：

override func viewDidLoad() {
    super.viewDidLoad()
    let timeSinceInstalled = -(installedDate ?? Date()).timeIntervalSinceNow
    Button1.isHidden = timeSinceInstalled < 604800
    Button2.isHidden = timeSinceInstalled < 2592000
    Button3.isHidden = timeSinceInstalled < 5184000
}

var installedDate: Date? {
    get {
        return UserDefaults.standard.object(forKey: "installedDateKey") as? Date
    }
    set {
        UserDefaults.standard.set(newValue, forKey: "installedDateKey")
    }
}

如果您想在按钮不可点击时将标题设置为 "You have none available"，代码如下：

override func viewDidLoad() {
    super.viewDidLoad()
    let timeSinceInstalled = -(installedDate ?? Date()).timeIntervalSinceNow
    setTitle(Button1, timeSinceInstalled < 604800)
    setTitle(Button2, timeSinceInstalled < 2592000)
    setTitle(Button3, timeSinceInstalled < 5184000)
}

func setTitle(_ button: UIButton, _ statement: Bool) {
    button.setTitle(statement ? "You have none available" : "Click me", for: .normal)
    button.isEnabled = !statement
}

var installedDate: Date? {
    get {
        return UserDefaults.standard.object(forKey: "installedDateKey") as? Date
    }
    set {
        UserDefaults.standard.set(newValue, forKey: "installedDateKey")
    }
}

Swift 4：使用日历检查自首次启动以来是否已过去一周、一个月、两个月等

Swift 4: Checking if week, month, 2 months, etc. has passed since initial launch using Calendar

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