Swift Codable解析keyNotFound

问题描述

我在编码方面遇到了问题。任何帮助将不胜感激。我在操场上有以下东西

I'm having an issue getting codable going. Any help would greatly appreciated. I have the following in my playground

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内容

I used the quicktype app to help generate the following structs

// 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?
}

快速代码：

 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。

This is the error message I get.

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，我不确定问题是什么。如果我从json和模型中删除了country-id，则对于country-iso也会收到相同的错误。

The value is there, I'm not sure what the issue is. If I take remove country-id from the json and model, I get the same error for country-iso.

推荐答案

您正在尝试解码错误的类型。 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 。

That's because you are trying to decode the wrong type. The CA type is nested several levels in your JSON, you need to pass the root type to JSONDecoder.decode.

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

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