Swift 3.0:将服务器 UTC 时间转换为本地时间，反之亦然 [英] Swift 3.0 : Convert server UTC time to local time and vice-versa

问题描述

我想将服务器 UTC 时间转换为本地时间，反之亦然.这是我的代码..

I want to convert server UTC time to local time and vice-versa. Here is my code..

var isTimeFromServer = true
var time:String!
var period:String!
let timeString = "6:59 AM" //Current UTC time

if isTimeFromServer {

    let index = timeString.index(timeString.startIndex, offsetBy: 5)
    let twelve = timeString.substring(to: index)

    var dateString:String!

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "H:mm"
    let date12 = dateFormatter.date(from: twelve)!

    dateFormatter.dateFormat = "h:mm a"
    let date22 = dateFormatter.string(from: date12)

    //print(date22)
    dateString = date22
    //print("dateString=\(dateString)")

    time = dateString.components(separatedBy: " ")[0]
    period = dateString.components(separatedBy: " ")[1]

}
else {
    time = timeString.components(separatedBy: " ")[0]
    period = timeString.components(separatedBy: " ")[1]
}

var hour = Int(time.components(separatedBy: ":")[0])

hour = period == "AM" ? hour : hour! + 12
let minute = Int(time.components(separatedBy: ":")[1])
let calender = NSCalendar.current
var datecomponent = DateComponents()
datecomponent.calendar = calender
datecomponent.hour = hour
datecomponent.minute = minute

if !isTimeFromServer {
    // local to UTC
    datecomponent.timeZone = TimeZone.current
}
else {
    datecomponent.timeZone = TimeZone(abbreviation: "UTC")
}

let date = datecomponent.date
let dateFormatter = DateFormatter()

if !isTimeFromServer {
    dateFormatter.dateFormat = "H:mm"
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
    dateFormatter.string(from: date!)
}
else {
    //UTC to local
    dateFormatter.dateFormat = "h:mm a"
    dateFormatter.timeZone = TimeZone.current
    dateFormatter.string(from: date!)
}

我得到当地时间

o/p:下午 12:52"

o/p: "12:52 PM"

但实际当地时间与输出时差为23分钟.

But actual local time and output time difference is 23 minutes.

推荐答案

我不知道你的代码有什么问题.
但是看起来有太多不必要的东西，比如你在设置日历，获取一些元素从字符串.这是我的 UTCToLocal 和 localToUTC 函数的小版本.
但为此，您需要以特定格式传递字符串.因为我强行打开了日期对象.但是您可以使用一些保护条件来防止您的应用程序崩溃.

I don't know what's wrong with your code.
But looks too much unnecessary things are there like you're setting calendar, fetching some elements from string. Here is my small version of UTCToLocal and localToUTC function.
But for that you need to pass string in specific format. Cause I've forcly unwrapped date objects. But you can use some guard conditions to prevent crashing your app.

func localToUTC(dateStr: String) -> String? {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "h:mm a"
    dateFormatter.calendar = Calendar.current
    dateFormatter.timeZone = TimeZone.current
    
    if let date = dateFormatter.date(from: dateStr) {
        dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
        dateFormatter.dateFormat = "H:mm:ss"
    
        return dateFormatter.string(from: date)
    }
    return nil
}

func utcToLocal(dateStr: String) -> String? {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "H:mm:ss"
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
    
    if let date = dateFormatter.date(from: dateStr) {
        dateFormatter.timeZone = TimeZone.current
        dateFormatter.dateFormat = "h:mm a"
    
        return dateFormatter.string(from: date)
    }
    return nil
}

并像下面这样调用这些函数.

and call these function like below.

print(utcToLocal(dateStr: "13:07:00"))
print(localToUTC(dateStr: "06:40 PM"))

希望这对您有所帮助.
编码愉快！

Hope this will help you.
Happy coding!!

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