ios - swift 4 可编码 : Converting JSON return String to Int/Date/Float

Question

我正在研究一些项目并删除 JSON 解析框架，因为使用 Swift 4 似乎很简单。我遇到了这个奇怪的 JSON 返回，其中 Ints 和 Dates 作为 Strings 返回。

我看了GrokSwift's Parsing JSON with Swift 4 , Apple's website ，但我没有看到任何关于 re: changing types 的内容。

Apple's example code显示了如何更改 key 名称，但我很难弄清楚如何更改 key 类型。

这是它的样子:

{
    "WaitTimes": [
        {
            "CheckpointIndex": "1",
            "WaitTime": "1",
            "Created_Datetime": "10/17/2017 6:57:29 PM"
        },
        {
            "CheckpointIndex": "2",
            "WaitTime": "6",
            "Created_Datetime": "10/12/2017 12:28:47 PM"
        },
        {
            "CheckpointIndex": "0",
            "WaitTime": "8",
            "Created_Datetime": "9/26/2017 5:04:42 AM"
        }
    ]
}

我使用 CodingKey 将字典键重命名为符合 Swift 的条目，如下所示:

struct WaitTimeContainer: Codable {
  let waitTimes: [WaitTime]

  private enum CodingKeys: String, CodingKey {
    case waitTimes = "WaitTimes"
  }

  struct WaitTime: Codable {
    let checkpointIndex: String
    let waitTime: String
    let createdDateTime: String

    private enum CodingKeys: String, CodingKey {
      case checkpointIndex = "CheckpointIndex"
      case waitTime = "WaitTime"
      case createdDateTime = "Created_Datetime"
    }
  }
}

这仍然给我留下了 String，它应该是 Int 或 Date。我将如何使用可编码协议(protocol)？

Answer 1

这是 not yet possible因为 Swift 团队在 JSONDecoder 中只提供了 String to date 解码器。

不过您始终可以手动解码:

struct WaitTimeContainer: Decodable {
    let waitTimes: [WaitTime]

    private enum CodingKeys: String, CodingKey {
        case waitTimes = "WaitTimes"
    }

    struct WaitTime:Decodable {
        let checkpointIndex: Int
        let waitTime: Float
        let createdDateTime: Date

        init(checkpointIndex: Int, waitTime: Float, createdDateTime:Date) {
            self.checkpointIndex = checkpointIndex
            self.waitTime = waitTime
            self.createdDateTime = createdDateTime
        }

        static let formatter: DateFormatter = {
            let formatter = DateFormatter()
            formatter.calendar = Calendar(identifier: .iso8601)
            formatter.locale = Locale(identifier: "en_US_POSIX")
            formatter.timeZone = TimeZone(secondsFromGMT: 0)
            formatter.dateFormat = "MM/dd/yyyy hh:mm:ss a"
            return formatter
        }()

        init(from decoder: Decoder) throws {
            let container = try decoder.container(keyedBy: CodingKeys.self)
            let checkpointIndexString = try container.decode(String.self, forKey: .checkpointIndex)
            let checkpointIndex = Int(checkpointIndexString)!

            let waitTimeString = try container.decode(String.self, forKey: .waitTime)
            let waitTime = Float(waitTimeString)!

            let createdDateTimeString =  try container.decode(String.self, forKey: .createdDateTime)

            let createdDateTime = WaitTime.formatter.date(from: createdDateTimeString)!

            self.init(checkpointIndex:checkpointIndex, waitTime:waitTime, createdDateTime:createdDateTime)
        }

        private enum CodingKeys: String, CodingKey {
            case checkpointIndex = "CheckpointIndex"
            case waitTime = "WaitTime"
            case createdDateTime = "Created_Datetime"
        }
    }
}