如何在iOS Swift Codable中通过API响应通知或打印模型类中缺少的键？

Question

我有一个来自API的JSON响应，如下所示，

以前的JSON响应：

[
  {
    "EmployeeId": 711,
    "FirstName": "Steve",
    "LastName": "Jobs"
  },
  {
    "EmployeeId": 714,
    "FirstName": "John",
    "LastName": "Doe"
  }
]

和model的模型类有以下代码

class EmployeeModel: Codable {

    let EmployeeId: Int?
    let FirstName: String?
    let LastName: String?
}

用Swift Codable解析工作正常

do {
    let decodedResponse = try JSONDecoder().decode([EmployeeModel].self, from: response.rawData())
    print(decodedResponse)

} catch let jsonErr {
    print(jsonErr.localizedDescription)
}

但现在

最新的JSON响应

从API更改并添加一个MiddleName键作为响应，请参阅下面的屏幕截图，它也可以正常使用Swift Codable代码。

但是如何在iOS Swift 5中通过API的JSON响应添加通知或打印MiddleName键？

更新问题

根据@ CZ54下面提供的答案，解决方案工作正常，但无法检查另一个派生类缺失键。 例如：

// MARK:- LoginModel
class LoginModel: Codable {

    let token: String?
    let currentUser: CurrentUser?
}

// MARK:- CurrentUser
class CurrentUser: Codable {

    let UserName: String?
    let EmployeeId: Int?
    let EmployeeName: String?
    let CompanyName: String?
}

Answer 1

您可以执行以下操作：

let json = """
    {
        "name" : "Jobs",
        "middleName" : "Bob"
    }
"""


class User: Decodable {
    let name: String
}
extension JSONDecoder {
    func decodeAndCheck<T>(_ type: T.Type, from data: Data) throws -> T where T : Decodable  {
       let result = try self.decode(type, from: data)

        if let json = try? JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions()) as? [String: Any] {
            let mirror = Mirror(reflecting: result)
            let jsonKeys = json.map { return $0.0 }
            let objectKeys = mirror.children.enumerated().map { $0.element.label }

            jsonKeys.forEach { (jsonKey) in
                if !objectKeys.contains(jsonKey) {
                    print("\(jsonKey) is not used yet")
                }
            }
        }
        return result

    }
}

try JSONDecoder().decodeAndCheck(User.self, from: json.data(using: .utf8)!)

//will print "middleName is not use yet"

Answer 2

您可以实现initializer并检查key是否存在，如下所示，

struct CustomCodingKey: CodingKey {

    let intValue: Int?
    let stringValue: String

    init?(stringValue: String) {
        self.intValue = Int(stringValue)
        self.stringValue = stringValue
    }

    init?(intValue: Int) {
        self.intValue = intValue
        self.stringValue = "\(intValue)"
    }
}

class EmployeeModel: Codable {

    var EmployeeId: Int?
    var FirstName: String?
    var LastName: String?

    private enum CodingKeys: String, CodingKey {
        case EmployeeId, FirstName, LastName
    }

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

        let allKeysContainer = try decoder.container(keyedBy: CustomCodingKey.self)

        self.EmployeeId = try container.decodeIfPresent(Int.self, forKey: .EmployeeId)
        self.FirstName = try container.decodeIfPresent(String.self, forKey: .FirstName)
        self.LastName = try container.decodeIfPresent(String.self, forKey: .LastName)

        let objectKeys = container.allKeys.map { $0.rawValue}
        for key in allKeysContainer.allKeys {
            if objectKeys.contains(key.stringValue) == false {
                print("Key: " + key.stringValue + " is added!")
            }
        }
    }
}