Swift4中更新数据库的两个日期比较

Question

我有这个代码：

func getSystemDate()-> String{
        let date = Date()
        let calendar = Calendar.current
        let hour = String(format: "%02d",calendar.component(.hour, from: date))
        let minutes = String(format: "%02d",calendar.component(.minute, from: date))
        let seconds = String(format: "%02d",calendar.component(.second, from: date))

        let day = String(format: "%02d",calendar.component(.day, from: date))
        let month = String(format: "%02d",calendar.component(.month, from: date))
        let year = String(format: "%02d",calendar.component(.year, from: date))

        let fullDate = "\(year)-\(month)-\(day) \(hour):\(minutes):\(seconds)"

        return fullDate
    }
let date1 = getSystemDate()
let date2 = "2018-05-23 13:14:47"

if date1 > date2 {
    print("its ok - update available")
} else {
    print("wrong - you have actually database")
}

我的函数 getSystemDate() returns 字符串中的实际日期。在变量 date2 中 - 我有数据库更新日期。

我需要确定是否可以更新数据库并将当前日期与可用数据库的日期进行比较：...

如何比较这些日期？

Answer 1

你可以用Calendar来比较两个Dates。您也可以转到 second unit，如果差异为 0 则表示它们相等，否则您可以检查哪个更大：

let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
//dateFormatter.timeZone   = TimeZone(abbreviation: "UTC")  // To add timezone

guard let dateOne = dateFormatter.date(from: "2018-05-23 13:14:47"), let dateTwo = dateFormatter.date(from: "2018-05-23 14:14:47") else {
    print("One of the date conversion is nil")
    return
}

print(dateOne, dateTwo)

let components = Calendar.current.dateComponents([.second], from: dateOne, to: dateTwo)
let secondsInBetween: Int = components.second!

print(secondsInBetween)

Swift4中更新数据库的两个日期比较

A comparison of two dates to update the database in Swift 4

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