Swift Codable解析keyNotFound

编程问答 2022-08-11

问题描述

我在编码方面遇到了问题。任何帮助将不胜感激。我的操场上有以下物品

我的JSON文件

{
"Metadata": {
  "generated": {
    "timestamp": 1549331723,"date": "2019-02-04 20:55:23"
  }
},"data": {
    "CA": {
    "country-id": 25000,"country-iso": "CA","country-eng": "Canada","country-fra": "Canada"
    }
  }
}

我使用quicktype应用程序来帮助生成以下结构

// MARK: - Welcome
struct Welcome: Codable {
    let Metadata: Metadata?
    let data: DataClass?
}

// MARK: - DataClass
struct DataClass: Codable {
    let ca: CA

    enum CodingKeys: String,CodingKey {
        case ca = "CA"
    }
}

// MARK: - CA
struct CA: Codable {
    let countryID: Int
    let countryISO,countryEng,countryFra: String

    enum CodingKeys: String,CodingKey {
        case countryID = "country-id"
        case countryISO = "country-iso"
        case countryEng = "country-eng"
        case countryFra = "country-fra"
    }
}

// MARK: - Metadata
struct Metadata: Codable {
    let generated: Generated?
}

// MARK: - Generated
struct Generated: Codable {
    let timestamp: Int?
    let date: String?
}

快捷代码：

 do {
        guard let url = Bundle.main.url(forResource: "data",withExtension: "json") else { return 0 }

        let jsonData = try Data(contentsOf: url)
        let decoder = JSONDecoder()

        let data = try decoder.decode(CA.self,from: jsonData)
        print (data)
        print(data.countryID)
        print(data.countryISO)
    } catch { print("error",error) }

这是我收到的错误消息。

jsonData 244 bytes
error keyNotFound(CodingKeys(stringValue: "country-id",intValue: nil),Swift.DecodingError.Context(codingPath: [],debugDescription: "No value associated with key CodingKeys(stringValue: \"country-id\",intValue: nil) (\"country-id\").",underlyingError: nil))

值在那里，我不确定是什么问题。如果我从json和模型中删除country-id，则对于country-iso也会收到相同的错误。

解决方法

那是因为您试图解码错误的类型。 CA类型在JSON中嵌套了多个级别，您需要将根类型传递给JSONDecoder.decode。

let root = try decoder.decode(Welcome.self,from: jsonData)
guard let ca = root.data?.ca else { return 0 }
print(ca)
codablejsonswiftswiftswift