Swift 4 Codable：将 JSON 返回字符串转换为 Int/Date/Float

Question

我正在经历一些项目并删除 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 返回为 Strings。

我查看了GrokSwift's Parsing JSON with Swift 4、Apple's website，但没有看到任何跳出的内容：改变类型。

Apple's example code 展示了如何更改键名，但我很难弄清楚如何更改键类型。

它是这样的：

{
    "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，应该是Int 或Date。如何使用 Codable 协议将包含 Int/Date/Float 作为 String 的 JSON 返回转换为 Int/Date/Float？

Answer 1

public extension KeyedDecodingContainer {
public func decode(_ type: Date.Type, forKey key: Key) throws -> Date {
    let dateString = try self.decode(String.self, forKey: key)
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "MM/dd/yyyy hh:mm:ss a"
    guard let date = dateFormatter.date(from: dateString) else {
        let context = DecodingError.Context(codingPath: codingPath,
                                            debugDescription: "Could not parse json key to a Date")
        throw DecodingError.dataCorrupted(context)
    }
    return date
}
}

用法：-

let date: Date = try container.decode(Date.self, forKey: . createdDateTime)

Answer 2

这是not yet possible，因为 Swift 团队在 JSONDecoder 中只提供了 String 到日期解码器。

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"
        }
    }
}