Swift可编码:如何将顶级数据编码到嵌套容器中

我的应用程序使用的服务器返回的json如下所示:

{
    "result":"OK",
    "data":{

        // Common to all URLs
        "user": {
            "name":"John Smith" // ETC...
        },

        // Different for each URL
        "data_for_this_url":0
    }
}

正如您所看到的,特定于URL的信息与公共资源存在于同一个词典中 user 字典。

目标:

1. 将此JSON解码为类/结构。
   • 因为 用户 是常见的,我希望它位于顶级类/结构中。
2. 编码为新格式(例如plist)。
   • 我需要保留原来的结构。(即重新创建 data 顶级词典 用户 信息和子对象的信息)

问题:

重新编码数据时,无法同时写入 用户 字典(从顶级对象)和特定于URL的数据(从子对象)到编码器。

要么 用户 覆盖其他数据或其他数据覆盖 用户 . 我不知道如何组合它们。

以下是我目前为止的情况:

// MARK: - Common User
struct User: Codable {
    var name: String?
}

// MARK: - Abstract Response
struct ApiResponse<DataType: Codable>: Codable {
    // MARK: Properties
    var result: String
    var user: User?
    var data: DataType?

    // MARK: Coding Keys
    enum CodingKeys: String, CodingKey {
        case result, data
    }
    enum DataDictKeys: String, CodingKey {
        case user
    }

    // MARK: Decodable
    init(from decoder: Decoder) throws {
        let baseContainer = try decoder.container(keyedBy: CodingKeys.self)
        self.result = try baseContainer.decode(String.self, forKey: .result)
        self.data = try baseContainer.decodeIfPresent(DataType.self, forKey: .data)

        let dataContainer = try baseContainer.nestedContainer(keyedBy: DataDictKeys.self, forKey: .data)
        self.user = try dataContainer.decodeIfPresent(User.self, forKey: .user)
    }

    // MARK: Encodable
    func encode(to encoder: Encoder) throws {
        var baseContainer = encoder.container(keyedBy: CodingKeys.self)
        try baseContainer.encode(self.result, forKey: .result)

        // MARK: - PROBLEM!!

        // This is overwritten
        try baseContainer.encodeIfPresent(self.data, forKey: .data)

        // This overwrites the previous statement
        var dataContainer = baseContainer.nestedContainer(keyedBy: DataDictKeys.self, forKey: .data)
        try dataContainer.encodeIfPresent(self.user, forKey: .user)
    }
}

例子:

在下面的示例中,重新编码的plist不包括 order_count ,因为它被包含 用户 .

// MARK: - Concrete Response
typealias OrderDataResponse = ApiResponse<OrderData>

struct OrderData: Codable {
    var orderCount: Int = 0
    enum CodingKeys: String, CodingKey {
        case orderCount = "order_count"
    }
}


let orderDataResponseJson = """
{
    "result":"OK",
    "data":{
        "user":{
            "name":"John"
        },
        "order_count":10
    }
}
"""

// MARK: - Decode from JSON
let jsonData = orderDataResponseJson.data(using: .utf8)!
let response = try JSONDecoder().decode(OrderDataResponse.self, from: jsonData)

// MARK: - Encode to PropertyList
let plistEncoder = PropertyListEncoder()
plistEncoder.outputFormat = .xml

let plistData = try plistEncoder.encode(response)
let plistString = String(data: plistData, encoding: .utf8)!

print(plistString)

// 'order_count' is not included in 'data'!

/*
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>data</key>
    <dict>
        <key>user</key>
        <dict>
            <key>name</key>
            <string>John</string>
        </dict>
    </dict>
    <key>result</key>
    <string>OK</string>
</dict>
</plist>
*/