json - 使用通配符键解析 JSON

Question

我正在解析一个设计不佳的 JSON 结构，我可以在其中找到被重用为指向更多数据的键的值。像这样

 {"modificationDate" : "..."
  "type" : "...",
  "version" : 2,
  "manufacturer": "<WILDCARD-ID>"

  "<WILDCARD-ID>": { /* known structure */ } }

WILDCARD-ID 在运行时几乎可以是任何东西，所以我无法在编译时将它映射到结构中某处的字段。但是一旦我取消引用该字段，它的值就具有已知结构，此时我可以按照通常的过程将 JSON 映射到 struct。

我发现自己正在走这条路

let json = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String: Any]
let manDict = json["manufacturer"]
let data = NSKeyedArchiver.archivedData(withRootObject: manDict)
// now you have data!

但这看起来很迂回，这让我觉得也许有更简洁的方法来完成这个？

Answer 1

您可以将自定义键与 Decodable 一起使用，如下所示:

let json = """
    {
        "modificationDate" : "...",
        "type" : "...",
        "version" : 2,
        "manufacturer": "<WILDCARD-ID>",
        "<WILDCARD-ID>": {
            "foo": 1
        }
    }
    """.data(using: .utf8)!

struct InnerStruct: Decodable { // just as an example
    let foo: Int
}

struct Example: Decodable {
    let modificationDate: String
    let type: String
    let version: Int
    let manufacturer: String
    let innerData: [String: InnerStruct]

    enum CodingKeys: String, CodingKey {
        case modificationDate, type, version, manufacturer
    }

    struct CustomKey: CodingKey {
        var stringValue: String
        var intValue: Int?
        init?(stringValue: String) {
            self.stringValue = stringValue
        }
        init?(intValue: Int) {
            self.stringValue = "\(intValue)";
            self.intValue = intValue
        }
    }

    init(from decoder: Decoder) throws {
        // extract all known properties
        let container = try decoder.container(keyedBy: CodingKeys.self)
        self.modificationDate = try container.decode(String.self, forKey: .modificationDate)
        self.type = try container.decode(String.self, forKey: .type)
        self.version = try container.decode(Int.self, forKey: .version)
        self.manufacturer = try container.decode(String.self, forKey: .manufacturer)

        // get the inner structs with the unknown key(s)
        var inner = [String: InnerStruct]()
        let customContainer = try decoder.container(keyedBy: CustomKey.self)
        for key in customContainer.allKeys {
            if let innerValue = try? customContainer.decode(InnerStruct.self, forKey: key) {
                inner[key.stringValue] = innerValue
            }
        }

        self.innerData = inner
    }
}

do {
    let example = try JSONDecoder().decode(Example.self, from: json)
    print(example)
}