swift - 从 timeZoneOffset 字符串创建 TimeZone 对象？

Question

什么是初始化 Swift 的干净方法 TimeZone来自 timeZoneOffset 字符串的对象，格式为:“+HH:MM”。

我正在寻找以下形式的内容:

extension TimeZone {

    init?(UTCOffsetString ofs: String) {

        let signIndex = ofs.firstIndex(of: "+") ?? ofs.firstIndex(of: "-")
        let sign = ofs[signIndex!]

        let separatorIndex = ofs.firstIndex(of: ":")!

        let hhRange = ofs.index(signIndex!, offsetBy: 1)..<separatorIndex
        let hh = ofs[hhRange]

        let mmRange = ofs.index(separatorIndex, offsetBy: 1)..<ofs.index(separatorIndex, offsetBy: 3)
        let mm = ofs[mmRange]

        var offsetInMin = (Int(String(hh))! * 60) + Int(String(mm))!
        if sign == "-" {
            offsetInMin.negate()
        }

        let offsetInSec = offsetInMin * 60
        // Convert string to TimeZone, eg.
        self.init(secondsFromGMT: offsetInSec)
    }

}

let tz = TimeZone.init(UTCOffsetString: "-07:30")
print(tz?.identifier ?? "unknown")

上面的代码块是一个正确的解决方案并打印:

GMT-0730

不过，我正在寻找一种更简洁的解决方案，我不需要提取子字符串来计算偏移量。

Answer 1

我的建议是使用能够解析时区字符串格式的DateFormatter。 refZoneString 是对当前时区 UTC 的引用。

extension TimeZone {

    init?(UTCOffsetString ofs: String) {
        let refZoneString = "+0000"
        let formatter = DateFormatter()
        formatter.dateFormat = "Z"
        guard let refDate = formatter.date(from: refZoneString),
            let date = formatter.date(from: ofs) else { return nil }
        self.init(secondsFromGMT: Calendar.current.dateComponents([.second], from: date, to: refDate).second!)
    }
}

let tz = TimeZone.init(UTCOffsetString: "-07:30")
print(tz?.identifier ?? "unknown")