Swift JSON解码报错：hourly_rate键不存在问题求助

API返回的JSON数据 #

[
    {
        "id": 1,
        "name": "instructor",
        "hourly_rate": 35.01,
        "bio": "Patient and experienced driving instructor specialising in new drivers",
        "profile_image": null,
        "rating": 4.8,
        "total_reviews": 25,
        "location": {
            "latitude": 51.5074,
            "longitude": -0.1278
        },
        "qualifications": [
            "ADI Certificate",
            "Grade A Instructor"
        ],
        "years_experience": 5,
        "gender": "female",
        "transmission": "Manual",
        "vehicle_type": null,
        "lesson_types": [
            "standard",
            "intensive",
            "pass_plus"
        ],
        "is_available": true
    }
]

Swift Instructor Codable模型 #

struct Instructor: Identifiable, Codable {
    let id: Int
    let name: String
    let rating: Double
    let hourlyRate: Double
    let experience: Int
    let profileImage: String?
    let description: String
    let availability: [Availability]
    let gender: InstructorGender
    let lessonTypes: [LessonType]
    let transmission: TransmissionType
    let vehicleType: String?
    let qualifications: [String]
    let isAvailable: Bool
    
    struct Availability: Codable {
        let dayOfWeek: Int
        let startTime: Date
        let endTime: Date
    }
    
    enum TransmissionType: String, Codable {
        case manual = "Manual"
        case automatic = "Automatic"
    }
    
    enum LessonType: String, Codable {
        case standard = "standard"
        case intensive = "intensive"
        case passPlus = "pass_plus"
    }
    
    enum InstructorGender: String, Codable {
        case male
        case female
        
        init(from decoder: Decoder) throws {
            let container = try decoder.singleValueContainer()
            let rawValue = try container.decode(String.self).lowercased()
            switch rawValue {
            case "male": self = .male
            case "female": self = .female
            default:
                throw DecodingError.dataCorruptedError(in: container, debugDescription: "Invalid gender value: \(rawValue)")
            }
        }
    }
    
    enum CodingKeys: String, CodingKey {
        case id
        case name
        case rating
        case hourlyRate = "hourly_rate"
        case experience = "years_experience"
        case profileImage = "profile_image"
        case description = "bio"
        case availability
        case gender
        case lessonTypes = "lesson_types"
        case transmission
        case vehicleType = "vehicle_type"
        case qualifications
        case isAvailable = "is_available"
    }
}

解码器与请求代码 #

private let jsonDecoder: JSONDecoder = {
        let decoder = JSONDecoder()
        decoder.dateDecodingStrategy = .iso8601
        decoder.keyDecodingStrategy = .convertFromSnakeCase
        return decoder
    }()
    

func getBookings(token: String) async throws -> [Booking] {
        guard let url = URL(string: "\(baseURL)/bookings") else {
            throw NetworkError.invalidURL
        }

        let data = try await sendAuthenticatedRequestWithData(to: url, method: .get, token: token)

        if let jsonString = String(data: data, encoding: .utf8) {
            print("📱 Raw Bookings JSON:", jsonString)
        }

        do {
            let bookings = try jsonDecoder.decode([Booking].self, from: data)
            print("📱 Successfully decoded \(bookings.count) bookings")
            return bookings
        } catch {
            print("❌ Decoding error: \(error)")
            throw error
        }
    }

错误信息（中文翻译） #

未找到键CodingKeys(stringValue: "hourly_rate", intValue: nil)，解码路径为[_JSONKey(stringValue: "Index 0", intValue: 0)]，调试描述：没有与键"hourly_rate"关联的值。

问题分析与解决方案 #

核心问题 #

1. 键解码策略冲突：同时设置了decoder.keyDecodingStrategy = .convertFromSnakeCase和手动CodingKeys映射，自动转换逻辑与手动映射冲突，导致解码器无法正确匹配字段。
2. 模型字段与JSON不匹配：Instructor模型中的availability字段在API返回的JSON中不存在，会触发解码失败。
3. 请求接口与模型不对应：调用的/bookings接口返回的是教练数据，却用[Booking].self解码，完全不匹配。

解决方案 #

• 统一键解码策略：保留.convertFromSnakeCase，简化CodingKeys，只保留非自动转换的映射（比如bio→description）：

  enum CodingKeys: String, CodingKey {
      case id, name, rating, hourlyRate, experience, profileImage
      case description = "bio"
      case availability, gender, lessonTypes, transmission, vehicleType, qualifications, isAvailable
  }
  

  此时hourly_rate会自动转为hourlyRate，无需手动映射。

• 处理不存在的字段：将模型中的availability改为可选类型，或直接删除该字段：

  let availability: [Availability]? // 改为可选类型
  

• 匹配接口与模型：修改请求方法，调用教练数据接口并解码[Instructor].self：

  func getInstructors(token: String) async throws -> [Instructor] {
      guard let url = URL(string: "\(baseURL)/instructors") else {
          throw NetworkError.invalidURL
      }
  
      let data = try await sendAuthenticatedRequestWithData(to: url, method: .get, token: token)
  
      if let jsonString = String(data: data, encoding: .utf8) {
          print("📱 Raw Instructors JSON:", jsonString)
      }
  
      do {
          let instructors = try jsonDecoder.decode([Instructor].self, from: data)
          print("📱 Successfully decoded \(instructors.count) instructors")
          return instructors
      } catch {
          print("❌ Decoding error: \(error)")
          throw error
      }
  }
  

内容的提问来源于stack exchange，提问作者user3524311