可编码解析问题答案

【问题标题】：Codable Parsing issue可编码解析问题
【发布时间】：2023-03-12 10:23:01
【问题描述】：

我正在尝试使用 Codable 类解析 API 响应。

下面是回复：

{"status":200,"message":"","success":1,"data":[{"event_id":"26","event_name":"Mens Night","event_desc":"Hot Mens Night","from_date":"2019-02-08","to_date":"2019-03-09","bar_id":"62","bar_names":"Autumn Bar & Bistro","bar_ids":"62","offer_image":"https:\/\/www.tippler.app\/manager\/uploads\/events\/mens_night.jpg","from_time":"19:00:00","to_time":"01:30:00"},{"event_id":"36","event_name":"Karaoke Night","event_desc":"Karaoke NIght with Brian Rub","from_date":"2019-02-08","to_date":"2019-02-09","bar_id":"146","bar_names":"Amuse Resto Bar","bar_ids":"146","offer_image":"https:\/\/www.tippler.app\/manager\/uploads\/events\/Screenshot_20190208-155223__011.jpg","from_time":"21:00:00","to_time":"01:00:00"},{"event_id":"37","event_name":"Sufi Nights","event_desc":"Singers From mumbai","from_date":"2019-02-08","to_date":"2019-02-09","bar_id":"66","bar_names":"Cavalry The Lounge","bar_ids":"66","offer_image":"https:\/\/www.tippler.app\/manager\/uploads\/events\/SUFI-FEATURED.jpg","from_time":"20:00:00","to_time":"01:30:00"},{"event_id":"39","event_name":"BOLLYWOOD NIGHT","event_desc":"BHANGRA AND LIVE DHOL","from_date":"2019-02-09","to_date":"2019-02-10","bar_id":"103","bar_names":"B Desi","bar_ids":"103","offer_image":"https:\/\/www.tippler.app\/manager\/uploads\/events\/bollywood-nights-1.jpg","from_time":"21:00:00","to_time":"01:00:00"}],"error_dev":""}

I Codable 类是：

struct Events: Codable {
    var event_id: String
    var event_name: String
    var event_desc: String
    var from_date: String
    var to_date: String
    var bar_id: String
    var bar_names: String
    var bar_ids: String
    var offer_image: String
    var from_time: String
    var to_time: String

    enum CodingKeys: String, CodingKey {
        case event_id = "event_id"
        case event_name = "event_name"
        case event_desc = "event_desc"
        case from_date = "from_date"
        case to_date = "to_date"
        case bar_id = "bar_id"
        case bar_names = "bar_names"
        case bar_ids = "bar_ids"
        case offer_image = "offer_image"
        case from_time = "from_time"
        case to_time = "to_time"
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(event_id, forKey: .event_id)
        try container.encode(event_name, forKey: .event_name)
        try? container.encode(event_desc, forKey: .event_desc)
        try? container.encode(from_date, forKey: .from_date)
        try container.encode(to_date, forKey: .to_date)
        try container.encode(bar_id, forKey: .bar_id)
        try container.encode(bar_names, forKey: .bar_names)
        try container.encode(bar_ids, forKey: .bar_ids)
        try container.encode(offer_image, forKey: .offer_image)
        try container.encode(from_time, forKey: .from_time)
        try container.encode(to_time, forKey: .to_time)
    }


    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        event_id = try values.decode(String.self, forKey: .event_id)
        event_name = try values.decode(String.self, forKey: .event_name)
        event_desc = try values.decode(String.self, forKey: .event_desc)
        from_date = try values.decode(String.self, forKey: .from_date)
        to_date = try values.decode(String.self, forKey: .to_date)
        bar_id = try values.decode(String.self, forKey: .bar_id)
        bar_names = try values.decode(String.self, forKey: .bar_names)
        bar_ids = try values.decode(String.self, forKey: .bar_ids)
        offer_image = try values.decode(String.self, forKey: .offer_image)
        from_time = try values.decode(String.self, forKey: .from_time)
        to_time = try values.decode(String.self, forKey: .to_time)
    }


}

它正在返回响应错误

keyNotFound(CodingKeys(stringValue: "event_id", intValue: nil), Swift.DecodingError.Context（编码路径： [编码键>（字符串值：“数据”，intValue：无）， _JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: \"event_id\", intValue: nil) (\"event_id\").", underlyingError: nil))

请给我建议解决方案。

【问题讨论】：

标签： json swift codable

【解决方案1】：

您的可编码结构与响应不匹配，因为它们具有状态、消息成功和 errorDev 键

试试这个

struct Response: Codable {
    let status: Int?
    let message: String?
    let success: Int?
    let data: [Events]?
    let errorDev: String?

    enum CodingKeys: String, CodingKey {
        case status, message, success, data
        case errorDev = "error_dev"
    }
}
struct Events: Codable {
    let eventID, eventName, eventDesc, fromDate: String?
    let toDate, barID, barNames, barIDs: String?
    let offerImage: String?
    let fromTime, toTime: String?

    enum CodingKeys: String, CodingKey {
        case eventID = "event_id"
        case eventName = "event_name"
        case eventDesc = "event_desc"
        case fromDate = "from_date"
        case toDate = "to_date"
        case barID = "bar_id"
        case barNames = "bar_names"
        case barIDs = "bar_ids"
        case offerImage = "offer_image"
        case fromTime = "from_time"
        case toTime = "to_time"
    }
}

编辑

我可以为您提供更通用的解决方案。假设所有 API 都具有相同的响应，但只有 data 键不同

struct GeneralResponse<T:Codable>: Codable {
     let status: Int?
     let message: String?
     let success: Int?
     let data: T?
     let errorDev: String?

    enum CodingKeys: String, CodingKey {
        case message = "msg"
        case code = "code"
        case data = "data" 
      // add more keys
    }

    public init(from decoder:Decoder) throws {
        let contaienr = try  decoder.container(keyedBy: CodingKeys.self)
        message = try contaienr.decode(String.self, forKey: .message)
        // Decode Other keys 

        do {
            let object = try contaienr.decodeIfPresent(T.self, forKey: .data)
            data = object

        } catch {
            data = nil
        }

    }

}

现在你可以回复每一个回复

使用GenericResponse<[Event]> 或GenericResponse<Login> 或GenericResponse<[UserList]>

希望对你有帮助

【讨论】：

将所有结构成员示意性地声明为可选是一个非常糟糕的建议。
@vadian 我不明白为什么，请你解释一下
API 发送的 JSON 实际上是一种非常可靠的格式。因此，首先您应该将所有结构成员声明为非可选，并通过将类型更改为可选来捕获并修复可能丢失的键的错误。另一方面，如果一切都是可选的并且出现问题，您将什么也看不到并且您不知道为什么。并且解包永远不会 nil 的选项非常烦人。
@vadian 是的，我明白这一点。我更喜欢使用可选的，因为 API 有可能没有发送参数（null），所以我没有处理错误，而是让可编码继续使用可选或 nil 值。后来我用必填字段处理这个。还有一件事是 API 可能包含许多不必要的字段，因此处理每个字段可能太长。并且可选，我们保证应用程序永远不会崩溃。

【解决方案2】：

struct Events : Codabel {
   let status: Int?
   let message: String?
   let success: Int?
   let data: [Event]?
   let errorDev: String?
}

struct Datum: Codable {
    let eventID, eventName, eventDesc, fromDate, offerImage, fromTime, toTime : String?
    let toDate, barID, barNames, barIDs: String?
}

无需为蛇类写下 CodingKeys，

解码时，你只需写

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
let responseModel = try decoder.decode(Events.self, from: data) // data from response

【讨论】：

将所有结构成员示意性地、轻率地声明为可选是一个非常糟糕的建议。
它返回 eventID 和 barID 为 nil

【解决方案3】：

您的代码中有几个错误如下...

event_id 在您的代码中属于 String 类型，但属于 Int 类型。
bar_id 在您的代码中属于 String 类型，但属于 Int 类型。
bar_ids 在您的代码中属于 String 类型，但属于 Int 类型。

您需要更正这些变量类型。

注意：无论您在哪里找到一个数字，它都会是 Int 类型，一个带有小数点的数字，例如 12.123 然后如果默认情况下将是 Double 类型。在swift中直接假设它是字符串是不可接受的。

【讨论】：