Swift

Question

我正在为项目创建和使用时基 UUID。我正在使用这个功能：

  class func timeBasedUUID() -> NSUUID {
    let uuidSize = sizeof(uuid_t)
    let uuidPointer = UnsafeMutablePointer<UInt8>.alloc(uuidSize)
    uuid_generate_time(uuidPointer)
    let uuid = NSUUID(UUIDBytes: uuidPointer)
    uuidPointer.dealloc(uuidSize)
    return uuid
  }

现在我想知道如何将它们从最旧到最新排序。我正在考虑比较字符串，但它是正确的吗？因为我不这么认为。

Answer 1

UUID 没有 "oldest" 或 "newest" 组件。确实 uuid_generate_time 使用时间来帮助保证 唯一性 ，但它并不是一种实际记录时间的方式。不要试图以这种方式滥用它。如果你知道你需要按日期对项目进行排序，你需要给他们一些额外的信息，例如。时间戳。

Answer 2

从 swift 中的 UUIDv1 解码时间戳：

extension UUID {
    static func timeBasedUUID() -> UUID? {
        let uuidSize = MemoryLayout<uuid_t>.size
        let uuidPointer = UnsafeMutablePointer<UInt8>.allocate(capacity: uuidSize)
        uuid_generate_time(uuidPointer)
        let uuid = uuidPointer.withMemoryRebound(to: uuid_t.self, capacity: 1) {
            return [=10=].pointee
        }

        uuidPointer.deallocate()
        return UUID(uuid: uuid)
    }

    var timestamp: TimeInterval {
        let components = uuidString.split(separator: "-")
        assert(components.count == 5)
        let hex = String(components[2].dropFirst()) + components[1] + components[0]
        // 100-nanoseconds intervals
        let interval = Int(hex, radix: 16)!
        let seconds = TimeInterval(interval / 10000000)

        // -12219292800 relative seconds to 1970
        return seconds - 12219292800
    }
}

参考文献：

Extracting the date and time a UUID was created
how do i get the date/time back from a UUID type 1
wikipedia

Swift - 基于时间的 UUID - 如何对它们进行排序

Swift - time based UUID - how to sort them

sorting

uuid

datetime

ios