从TimeZone.abbreviation()初始化TimeZone时出现问题

Question

我存储用户的出生日期在我的后端通过存储日期组件字典。它看起来像这样：

{
    "day": 1,
    "month": 1,
    "year": 1970,
    "timeZone": "GMT"
}

为了存储这个对象，它从用户输入中获取用户的出生日期、月份和年份。但是，用户时区是通过TimeZone.current.abbreviation()收集的。

现在，我的后端上的一些用户生日对象的"timeZone"格式为"CST"、"BST"或"PDT"。以这种方式格式化的"timeZone"分别通过let timeZone = TimeZone(abbreviation: "CST")!、let timeZone = TimeZone(abbreviation: "BST")!或let timeZone = TimeZone(abbreviation: "PDT")!在前端成功初始化TimeZone。

问题是，我的后端上的其他用户生日对象将其"timeZone"格式化为"GMT+8"。当尝试通过let timeZone = TimeZone(abbreviation: "GMT+8")!初始化格式为这样的"timeZone"时，初始化返回nil。我也尝试过let timeZone = TimeZone(identifier: "GMT+8")!，但这也返回了nil。

有没有一种方法可以在格式化TimeZone时初始化它，它的偏移量是GMT，而不是它唯一的缩写？我见过一个名为TimeZone(secondsFromGMT: Int)的TimeZone初始化器。我是否可以简单地将"GMT+8"中的8乘以3600 (一小时内的秒数)并将结果传递给TimeZone(secondsFromGMT: Int)

Answer 1

我最终编写了代码来调整我的应用程序，以应对这些意外的边缘情况，其中时区的缩写格式为"GMT+8"而不是"SGT"。我为TimeZone创建了一个扩展

extension TimeZone {
    static func timeZone(from string: String) -> TimeZone {
        //The string format passed into this function should always be similar to "GMT+8" or "GMT-3:30"

        if string.contains("±") {
            //This case should always be "GMT±00:00", or simply GMT
            return TimeZone(secondsFromGMT: 0)!
        } else {

            //If the string doesn't contain "±", then there should be some offset. We will split the string into timeZone components. "GMT+8" would split into ["GMT", "8"]. "GMT-3:30" would split int ["GMT","3","30"]
            let timeZoneComponents = string.components(separatedBy: CharacterSet(charactersIn: "+-:"))
            var isAheadOfGMT: Bool!

            //Check if the string contains "+". This will dictate if we add or subtract seconds from GMT
            if string.contains("+") {
                isAheadOfGMT = true
            } else {
                isAheadOfGMT = false
            }

            //Grab the second element in timeZoneElements. This represents the offset in hours
            let offsetInHours = Int(timeZoneComponents[1])!

            //Convert these hours into seconds
            var offsetInSeconds: Int!
            if isAheadOfGMT {
                offsetInSeconds = offsetInHours * 3600
            } else {
                offsetInSeconds = offsetInHours * -3600
            }

            //Check if there is a colon in the passed string. If it does, then there are additional minutes we need to account for
            if string.contains(":") {
                let additionalMinutes = Int(timeZoneComponents[2])!
                let additionalSeconds = additionalMinutes * 60
                offsetInSeconds += additionalSeconds
            }

            //Create a TimeZone from this calculated offset in seconds
            let timeZoneFromOffset = TimeZone(secondsFromGMT: offsetInSeconds)!

            //Return this value
            return timeZoneFromOffset
        }
    }
}

它的用法如下：

let json: [String:String] = ["timeZone":"GMT+8"]
let timeZone = json["timeZone"]
let birthDate: BirthDate!
if let timeZoneFromAbbrev = TimeZone(abbreviation: timeZone) {
    birthDate = BirthDate(day: birthDay, month: birthMonth, year: birthYear, timeZone: timeZoneFromAbbrev)
} else {       
    let timeZoneFromOffset = TimeZone.timeZone(from: timeZone)
    print(timeZoneFromOffset.abbreviation())
    //Prints "GMT+8"

    birthDate = BirthDate(day: birthDay, month: birthMonth, year: birthYear, timeZone: timeZoneFromOffset)
}

我的上下文BirthDate类：

class BirthDate {
    var day: Int
    var month: Int
    var year: Int
    var timeZone: TimeZone

    init(day: Int, month: Int, year: Int, timeZone: TimeZone) {
        self.day = day
        self.month = month
        self.year = year
        self.timeZone = timeZone
    }
}

使用时区是很有趣的事情。如果有人在上面看到TimeZone扩展的问题，请让我知道。我想我已经考虑了所有的情况，但可能是错误的。