Any when decoding JSON with Codable?

Question

With Swift 3 JSONSerialization, if a part of your data model was completely dynamic, you could always just leave the deserialized data at Any and l

Answer 1

I solved my problem creating an AnyValue struct to allow Encode and Decode Any values from JSON:

To use it is pretty simple:

class MyClass: Codable {

    var data: [String: AnyValue?]?

    init(data: [String: AnyValue?]) {
        self.data = data
    }
}


let data = ["a": AnyValue(3), "b": AnyValue(true), "c": AnyValue("Rodrigo"), "d": AnyValue(3.3)]
let myClass = MyClass(data: data)

if let json = JsonUtil.toJson(myClass) {
    print(json) // {"data":{"d":3.3,"b":true,"c":"Rodrigo","a":3}}

    if let data = JsonUtil.from(json: json)?.data {
        print(data["a"]??.value() ?? "nil") // 3
        print(data["b"]??.value() ?? "nil") // true
        print(data["c"]??.value() ?? "nil") // Rodrigo
        print(data["d"]??.value() ?? "nil") // 3.3
    }
}

AnyValue struct:

struct AnyValue: Codable {

    private var int: Int?
    private var string: String?
    private var bool: Bool?
    private var double: Double?

    init(_ int: Int) {
        self.int = int
    }

    init(_ string: String) {
        self.string = string
    }

    init(_ bool: Bool) {
        self.bool = bool
    }

    init(_ double: Double) {
        self.double = double
    }

    init(from decoder: Decoder) throws {
        if let int = try? decoder.singleValueContainer().decode(Int.self) {
            self.int = int
            return
        }

        if let string = try? decoder.singleValueContainer().decode(String.self) {
            self.string = string
            return
        }

        if let bool = try? decoder.singleValueContainer().decode(Bool.self) {
            self.bool = bool
            return
        }

        if let double = try? decoder.singleValueContainer().decode(Double.self) {
            self.double = double
        }
    }


    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()

        if let anyValue = self.value() {
            if let value = anyValue as? Int {
                try container.encode(value)
                return
            }

            if let value = anyValue as? String {
                try container.encode(value)
                return
            }

            if let value = anyValue as? Bool {
                try container.encode(value)
                return
            }

            if let value = anyValue as? Double {
                try container.encode(value)
                return
            }
        }

        try container.encodeNil()
    }


    func value() -> Any? {
        return self.int ?? self.string ?? self.bool ?? self.double
    }
}

And I created a JsonUtil struct too:

struct JsonUtil  {

    public static func from(json: String) -> T? {
        if let jsonData = json.data(using: .utf8) {
            let jsonDecoder = JSONDecoder()

            do {
                return try jsonDecoder.decode(T.self, from: jsonData)

            } catch {
                print(error)
            }
        }

        return nil
    }

    public static func toJson(_ obj: T) -> String? {
        let jsonEncoder = JSONEncoder()

        do {
            let jsonData = try jsonEncoder.encode(obj)
            return String(data: jsonData, encoding: String.Encoding.utf8)

        } catch {
            print(error)
            return nil
        }
    }
}

If you need a new type like [String] per example, you just need add it on AnyValue struct.

Good luck :)