在Swift中采用FIRGeoPoint到Codable协议

我有一个Firebase Firestore文档，其中包含String，Number和GeoPoint值 . 这是由print（）函数打印的示例控制台输出 .

[
  "name": "Test", 
  "location": <FIRGeoPoint: (37.165300, 27.590800)>, 
  "aNumber": 123123
]

现在我想为这个文档创建一个结构，符合 Codable 协议 .

struct TestStruct: Codable {

  let name: String
  let aNumber: Double
  let location: GeoPoint

  struct CodingKeys: CodingKey {
    case name, location, aNumber
  }

  init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)

    name = try container.decode(String.self, forKey: CodingKeys.name)
    aNumber = try container.decode(Double.self, forKey: CodingKeys.aNumber)
    location = try container.decode(GeoPoint.self, forKey: CodingKeys.location)
  }
}

// encode is not implemented yet.

此代码将显示错误，因为GeoPoint不符合Codable协议 .

所以我试着让GeoPoint符合Codable：

extension GeoPoint: Codable {

  enum CodingKeys: CodingKey {
    case latitute, longitude
  }

  public required init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    let latitude = try container.decode(Double.self, forKey: CodingKeys.latitute)
    let longitude = try container.decode(Double.self, forKey: CodingKeys.latitute)

    super.init(latitude: latitude, longitude: longitude)
  }

  func encode(to encoder: Encoder) throws {
    var container = encoder.container(keyedBy: CodingKeys.self)
    try container.encode(latitude, forKey: CodingKeys.latitute)
    try container.encode(longitude, forKey: CodingKeys.longitude)
  }
}

现在，IDE对我很生气！

初始值设定项 init(from:) 应为 required ，但扩展名不能包含所需的初始值设定项 . 此外，扩展名不能指定初始化程序，因此初始化程序也应该是 convenience . 一个愚蠢的死胡同 .

为了绕过它，我将GeoPoint子类化：

class ANGeoPoint: GeoPoint, Codable {

  enum CodingKeys: CodingKey {
    case latitute, longitude
  }

  public required init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    let latitude = try container.decode(Double.self, forKey: CodingKeys.latitute)
    let longitude = try container.decode(Double.self, forKey: CodingKeys.latitute)

    super.init(latitude: latitude, longitude: longitude)
  }

  func encode(to encoder: Encoder) throws {
    var container = encoder.container(keyedBy: CodingKeys.self)
    try container.encode(latitude, forKey: CodingKeys.latitute)
    try container.encode(longitude, forKey: CodingKeys.longitude)
  }
}

并改变了

location = try container.decode(GeoPoint.self, forKey: CodingKeys.location)

到

location = try container.decode(ANGeoPoint.self, forKey: CodingKeys.location)

现在代码清除了IDE警告 . 我们来试试吧：

Firestore.firestore()
    .collection("testCollection")
    .document("qweasdzxc")
    .getDocument { (snap, error) in
        if let data = snap?.data() {
            let jsonData = JSONSerialization.data(withJSONObject: data, options: .prettyPrinted)
            let myStruct = try? JSONDecoder().decode(TestStruct.self, from: jsonData)
        } 
}

当我们运行我们的测试代码时，它会破坏！这是我全新的婴儿运行时错误：

由于未捕获的异常'NSInvalidArgumentException'终止应用程序，原因：'JSON写入中的无效类型（FIRGeoPoint）'

让我们回顾一下示例数据的控制台输出：

... "location": <FIRGeoPoint: (37.165300, 27.590800)> ...

即使我尝试将 location 解码为ANGeoPoint，同时将数据解码为TestStruct， the location data coming from Firestore is still GeoPoint . 并且JSONDecode无法解码非Codable对象 .

更多，因为你记得Xcode不让我创建一个Codable GeoPoint .

现在我被卡住了！有什么建议？谢谢 .

编辑：我在Firebase iOS SDK中找到了这个：https://github.com/firebase/firebase-ios-sdk/commit/13e366738463739f0c21d4cedab4bafbfdb57c6f

但即使我使用的是最新版本，我的代码也没有 . 所以我手动添加：

protocol CodableGeoPoint: Codable {
  var latitude: Double { get }
  var longitude: Double { get }

  init(latitude: Double, longitude: Double)
}

extension CodableGeoPoint {
  public init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    let latitude = try container.decode(Double.self, forKey: CodingKeys.makeKey(name: "latitude"))
    let longitude = try container.decode(Double.self, forKey: CodingKeys.makeKey(name: "longitude"))

    self.init(latitude: latitude, longitude: longitude)
  }

  public func encode(to encoder: Encoder) throws {
    var container = encoder.container(keyedBy: CodingKeys.self)
    try container.encode(latitude, forKey: CodingKeys.makeKey(name: "latitude"))
    try container.encode(longitude, forKey: CodingKeys.makeKey(name: "longitude"))
  }
}

extension GeoPoint: CodableGeoPoint {}

现在 GeoPoint 是Codable . 但我仍然无法用JSONDecoder解码它 .