Swift 4：检查周、月、2 个月等自使用日历首次启动以来是否已过去

Question

我正在尝试包含计时器，以便在应用程序的初始启动日期后一周、一个月、2 个月等出现按钮。

我使用过Date.addingTimeInterval（请参见下面的代码），但在较长的时间段（周/月）内似乎效果不佳。 Swift 文档建议使用日历，但我不知道该怎么做。

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")
        }
    }

比较发布日期和我需要的预期日期的更有效方法是什么？

Answer 1

根据我对您的问题的了解，如果他们使用该应用的时间超过一定时间，您希望显示一个按钮。如果是这样，我已经编写了一些对您有帮助的代码：

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，甚至是您检查 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“您没有可用的”，则代码如下：

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")
    }
}