Ios 如何用多个链接URL请求和请求依赖项填充单个模型对象？

我有一个数据模型对象，我必须填充多个网络请求

我的模型看起来像这样

struct CO2Data: Identifiable, Codable {
    let id = UUID()
    let totalCO2: Double
    let dailyAverage: Int
    let calendar = Calendar.current
    let dateString: String
    let emissionStats: EmissionStats

let driveLog: String 
    // It is an ID to get the trip details

    let trip : Trip
    // This is what needs to be filled from the next URL request using driveLog


    enum CodingKeys: String, CodingKey {
        case id
        case totalCO2 = "totCO2"
        case dateString = "stDt"
        case dailyAverage = "avg"
        case emissionStats = "emisStats"
        case drLogRefId = "drLogRefId"
        //Not having case trip here breaks the conformance to codable
        // and results in error
    }
}

// for CO2Data
[
  {
    "stDt": "2019-11-17T16:00:00.000+0000",
    "totCO2": 50,
    "avg": 0,
    "emisStats": {
      "wea": 10,
      "aggDr": 10,
      "tfc": 10,
      "tirePress": 0,
      "ac": 10,
      "seatHeater": 10
    },
    "drLogRefId": "5dc20204199f752c7726a8f0"
  }
]

//for Trip
[
  {
    "id": "5dc20204199f752c7726a8f0",
    "startTime": "...",
    "startLat: "...",
    "startLong: "...",
    "endLat: "...",
    "endLong": "...",
  }
]

这是网络请求和响应的流程

请求获取CO2Data并使用JSONDecoder（）对其进行解码

使用获取的CO2数据中的driveLog属性发出另一个网络请求以获取Trip对象

第二次网络请求的结果应添加到trip属性中的CO2Data对象中

我该怎么做呢。甚至可以将行程存储在CO2数据中吗

我正在使用Combine&URLSession.shared.dataTaskPublisher（for:URLRequest）进行此操作，但我完全可以使用普通的简单数据任务。 有没有像这样处理请求依赖关系的已知方法？ 我不使用任何第三方库，希望坚持使用URLSession

JSON对象如下所示

struct CO2Data: Identifiable, Codable {
    let id = UUID()
    let totalCO2: Double
    let dailyAverage: Int
    let calendar = Calendar.current
    let dateString: String
    let emissionStats: EmissionStats

let driveLog: String 
    // It is an ID to get the trip details

    let trip : Trip
    // This is what needs to be filled from the next URL request using driveLog


    enum CodingKeys: String, CodingKey {
        case id
        case totalCO2 = "totCO2"
        case dateString = "stDt"
        case dailyAverage = "avg"
        case emissionStats = "emisStats"
        case drLogRefId = "drLogRefId"
        //Not having case trip here breaks the conformance to codable
        // and results in error
    }
}

// for CO2Data
[
  {
    "stDt": "2019-11-17T16:00:00.000+0000",
    "totCO2": 50,
    "avg": 0,
    "emisStats": {
      "wea": 10,
      "aggDr": 10,
      "tfc": 10,
      "tirePress": 0,
      "ac": 10,
      "seatHeater": 10
    },
    "drLogRefId": "5dc20204199f752c7726a8f0"
  }
]

//for Trip
[
  {
    "id": "5dc20204199f752c7726a8f0",
    "startTime": "...",
    "startLat: "...",
    "startLong: "...",
    "endLat: "...",
    "endLong": "...",
  }
]

---

根据周围数据的复杂性，查看

• 操作：您可以指定此操作所依赖的其他操作
• DispatchGroup：使用

  DispatchGroup.enter（）

  ，

  DispatchGroup.leave（）

  和最后的

  DispatchGroup.notify（）

  还可以对所执行的已调度任务的依赖关系建模

---

祝你好运

以下是实现目标的方法。在第一次网络呼叫期间，您需要将

Trip

设置为可选，因为您没有要在那里设置的数据。确保在json解码期间正确处理此问题

然后使用

flatMap

进行第二次网络调用。 使用

zip

等待两个请求完成，并将结果数据传递给扩展

CO2Data.init

完整代码，其中fetchCO2TripData将返回CO2Data和Trip：

struct CO2Data: Identifiable, Codable {
    let id = UUID()
    /// TODO: add other properties
    let driveLog: String
    let trip : Trip?
}

struct Trip: Codable {
    let startTime: String
    let endTime: String
    let startLat: String
    let startLong: String
    let endLat: String
    let endLong: String
}

func fetchCO2Data() -> AnyPublisher<CO2Data, Error> {
    /// TODO: Replace with actual network request
    Empty().eraseToAnyPublisher()
}

func fetchTripData(by driveLog: String) -> AnyPublisher<Trip, Error> {
    /// TODO: Replace with actual network request
    Empty().eraseToAnyPublisher()
}

func fetchCO2TripData() -> AnyPublisher<CO2Data, Error> {
    let co2Publisher = fetchCO2Data().share()
    let tripPublisher = co2Publisher.flatMap { fetchTripData(by: $0.driveLog) }

    return co2Publisher
        .zip(tripPublisher)
        .map { CO2Data(co2data: $0, trip: $1) }
        .eraseToAnyPublisher()
}

extension CO2Data {
    init(co2data: CO2Data, trip: Trip) {
        self.driveLog = co2data.driveLog
        self.trip = trip
    }
}