date - 如何在 Swift 中解析/创建格式为小数秒 UTC 时区(ISO 8601、RFC 3339)的日期时间戳？

Question

如何使用 ISO 8601 的格式标准生成日期时间戳记和 RFC 3339 ？

目标是一个如下所示的字符串:

"2015-01-01T00:00:00.000Z"

格式:

• 年、月、日，如“XXXX-XX-XX”
• 字母“T”作为分隔符
• 时、分、秒、毫秒，如“XX:XX:XX.XXX”。
• 字母“Z”作为零偏移的区域指示符，又称 UTC、GMT、Zulu 时间。

最好的情况:

• Swift 源代码简单、简短、直接。
• 无需使用任何额外的框架、子项目、cocoapod、C 代码等。

我搜索了 StackOverflow、Google、Apple 等，但没有找到对此问题的 Swift 答案。

看起来最有前途的类是 NSDate , NSDateFormatter , NSTimeZone .

相关问答:How do I get an ISO 8601 date on iOS?

这是迄今为止我想到的最好的:

var now = NSDate()
var formatter = NSDateFormatter()
formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
formatter.timeZone = NSTimeZone(forSecondsFromGMT: 0)
println(formatter.stringFromDate(now))

Answer 1

Swift 4 • iOS 11.2.1 或更高版本

extension ISO8601DateFormatter {
    convenience init(_ formatOptions: Options) {
        self.init()
        self.formatOptions = formatOptions
    }
}

<小时/>

extension Formatter {
    static let iso8601withFractionalSeconds = ISO8601DateFormatter([.withInternetDateTime, .withFractionalSeconds])
}

<小时/>

extension Date {
    var iso8601withFractionalSeconds: String { return Formatter.iso8601withFractionalSeconds.string(from: self) }
}

<小时/>

extension String {
    var iso8601withFractionalSeconds: Date? { return Formatter.iso8601withFractionalSeconds.date(from: self) }
}

<小时/>

用法:

Date().description(with: .current)  //  Tuesday, February 5, 2019 at 10:35:01 PM Brasilia Summer Time"
let dateString = Date().iso8601withFractionalSeconds   //  "2019-02-06T00:35:01.746Z"

if let date = dateString.iso8601withFractionalSeconds {
    date.description(with: .current) // "Tuesday, February 5, 2019 at 10:35:01 PM Brasilia Summer Time"
    print(date.iso8601withFractionalSeconds)           //  "2019-02-06T00:35:01.746Z\n"
}

<小时/>

iOS 9 • Swift 3 或更高版本

extension Formatter {
    static let iso8601withFractionalSeconds: DateFormatter = {
        let formatter = DateFormatter()
        formatter.calendar = Calendar(identifier: .iso8601)
        formatter.locale = Locale(identifier: "en_US_POSIX")
        formatter.timeZone = TimeZone(secondsFromGMT: 0)
        formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSXXXXX"
        return formatter
    }()
}

<小时/>

Codable Protocol

If you need to encode and decode this format when working with Codable protocol you can create your own custom date encoding/decoding strategies:

extension JSONDecoder.DateDecodingStrategy {
    static let iso8601withFractionalSeconds = custom {
        let container = try $0.singleValueContainer()
        let string = try container.decode(String.self)
        guard let date = Formatter.iso8601withFractionalSeconds.date(from: string) else {
            throw DecodingError.dataCorruptedError(in: container,
                  debugDescription: "Invalid date: " + string)
        }
        return date
    }
}

以及编码策略

extension JSONEncoder.DateEncodingStrategy {
    static let iso8601withFractionalSeconds = custom {
        var container = $1.singleValueContainer()
        try container.encode(Formatter.iso8601withFractionalSeconds.string(from: $0))
    }
}

<小时/>

Playground 测试

let dates = [Date()]   // ["Feb 8, 2019 at 9:48 PM"]

编码

let encoder = JSONEncoder()
encoder.dateEncodingStrategy = .iso8601withFractionalSeconds
let data = try! encoder.encode(dates)
print(String(data: data, encoding: .utf8)!)

解码

let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601withFractionalSeconds
let decodedDates = try! decoder.decode([Date].self, from: data)  // ["Feb 8, 2019 at 9:48 PM"]