Swift中URLSession结合Combine解码JSON数组失败问题解决

调用服务接口时获取到JSON数组，但无法通过Combine的URLSession.shared.dataTaskPublisher完成解码。项目采用Data、Domain、Presentation分层架构（基于GitHub上的CiMA混合Viper架构）。

原请求代码：

public func getGasStationDiscounts(requestModel: GasStationDiscountsRequestDomainModel) -> CiMAObservable<GasStationDiscountsDomainModel> {
    guard let url = URL(string: RepositoryConstants.baseURL + String(format: RepositoryConstants.EndPoints.gasStationDiscounts, requestModel.gasStationID)) else {
        return Fail(error: NSError(domain: "URL Invalid", code: 001, userInfo: nil)).eraseToAnyPublisher()
    }
    
    var urlRequest = URLRequest(url: url)
    urlRequest.httpMethod = "GET"
    urlRequest.addValue("application/json", forHTTPHeaderField: "Accept")
    urlRequest.addValue("application/json", forHTTPHeaderField: "Content-Type")
    
    return URLSession.shared.dataTaskPublisher(for: urlRequest)
        .map(\.data)
        .decode(type: GasStationDiscountsDataModel.self, decoder: JSONDecoder())
        .map { model -> GasStationDiscountsDomainModel in
            model.parseToDomainModel()
        }.eraseToAnyPublisher()
}

原可解码模型说明：
原GasStationDiscountsDataModel是针对单个对象的解码模型，但接口实际返回的是该对象组成的JSON数组，导致解码结构不匹配。

已解决！
找到不破坏现有架构的解决方案，调整如下：

可解码模型修改 #

将原GasStationDiscountsDataModel调整为对应数组中单个元素的结构，确保其能正确解码数组内的每一项数据。

修改后的请求代码 #

public func getGasStationDiscounts(requestModel: GasStationDiscountsRequestDomainModel) -> CiMAObservable<GasStationDiscountsDomainModel> {
    guard let url = URL(string: RepositoryConstants.baseURL + String(format: RepositoryConstants.EndPoints.gasStationDiscounts, requestModel.gasStationID)) else {
        return Fail(error: NSError(domain: "URL Invalid", code: 001, userInfo: nil)).eraseToAnyPublisher()
    }
    
    var urlRequest = URLRequest(url: url)
    urlRequest.httpMethod = "GET"
    urlRequest.addValue("application/json", forHTTPHeaderField: "Accept")
    urlRequest.addValue("application/json", forHTTPHeaderField: "Content-Type")
    
    return URLSession.shared.dataTaskPublisher(for: urlRequest)
        .map(\.data)
        .decode(type: [GasStationDiscountsDataModel].self, decoder: JSONDecoder())
        .map { model -> GasStationDiscountsDomainModel in
            let stationDiscountsDomainModel = model.map { model -> StationDiscountDomainModel in
                model.parseToDomainModel()
            }
            return GasStationDiscountsDomainModel(stationDiscounts: stationDiscountsDomainModel)
        }
        .mapError { error in
            print(error.localizedDescription)
            return error
        }.eraseToAnyPublisher()
}

关键修改点 #

1. 解码类型从GasStationDiscountsDataModel.self改为[GasStationDiscountsDataModel].self，匹配接口返回的数组结构
2. 在map操作中遍历解码后的数组，将每个DataModel转换为对应的DomainModel，再封装到GasStationDiscountsDomainModel中，适配分层架构要求
3. 添加mapError处理，便于调试解码过程中的错误

内容的提问来源于stack exchange，提问作者coden0w