从 TimeZone.abbreviation() 初始化 TimeZone 时遇到问题

Question

我通过存储日期组件字典在后端存储用户出生日期。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生日、月份和年份。但是，用户时区是通过TimeZone.current.abbreviation() 收集的。

现在，我后端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"s 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，我后端的其他用户生日对象的"timeZone" 格式为"GMT+8"。当尝试通过let timeZone = TimeZone(abbreviation: "GMT+8")! 初始化像这样格式化的"timeZone"s 时，初始化返回nil。我也试过let timeZone = TimeZone(identifier: "GMT+8")!，但这也返回nil。

当TimeZone 的格式是相对于其与 GMT 的偏移量而不是其唯一的缩写时，有没有办法初始化它？我见过TimeZone 初始化程序是TimeZone(secondsFromGMT: Int)。我可以简单地从"GMT+8" 中取出8 并乘以3600（一小时的秒数）并将这个结果传递给TimeZone(secondsFromGMT: Int)？

Answer 1

我最终编写了代码来调整我的应用程序，以解决这些意外的边缘情况，其中 TimeZone 的缩写格式类似于 "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
        }
    }
}

它是这样使用的：

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BirthDate 上下文类：

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
    }
}

时区是很有趣的事情。如果有人发现上面的 TimeZone 扩展存在问题，请告诉我。我想我已经考虑了所有情况，但可能会出错。