iOS Swift - 计算两次之间的差异

Question

我想知道如何计算登录时间和注销时间之间的差异，例如：登录时间：上午 8:00 和注销时间：下午 5:00，我应该得到 9 小时作为总小时数渲染。

这是保存到 Firebase 的时间格式

     // Set the time
    let timeFormatter = DateFormatter()
    timeFormatter.dateStyle = .none
    timeFormatter.timeStyle = .short
    timeFormatter.amSymbol = "AM"
    timeFormatter.pmSymbol = "PM"

    let timeString = timeFormatter.string(from: date)

Answer 1

编辑： Found duplicate question

从登录 (loginTime) 和注销 (logoutTime) 时间创建 Date 对象 (link to question)，然后像这样使用它们：

let components = Calendar.current.dateComponents([.hour, .minute], from: loginTime, to: logoutTime)

// To get the hours
print(components.hour)
// To get the minutes
print(components.minute)

Answer 2

登录时...

    let loginTime = Date()
    UserDefaults.standard.set(loginTime, forKey: "loginTime")

然后在注销时...

    let loginTime = UserDefaults.standard.object(forKey: "loginTime") as? Date ?? Date()
    let loginInterval = -loginTime.timeIntervalSinceNow

    let formatter = DateComponentsFormatter()
    formatter.unitsStyle = .full
    formatter.includesApproximationPhrase = false
    formatter.includesTimeRemainingPhrase = false
    formatter.allowedUnits = [.hour, .minute]

    // Use the configured formatter to generate the string.
    let userLoginTimeString = formatter.string(from: loginInterval) ?? ""
    print("user was logged in for \(userLoginTimeString)")