This protocol combined Codable and Equatable. It can convert to JSON and compare it, or it can return Dictionary type.

//
// Jsonable.swift
//
// MIT License
//
// Copyright (c) 2018 makietan
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

import Foundation

protocol Jsonable: Codable, Equatable {
}

extension Jsonable {

    public static func ==(lhs: Self, rhs: Self) -> Bool {
        return lhs.toJson() == rhs.toJson()
    }

    func toDictionary() -> [String: Any] {
        guard let jsonData = try? JSONEncoder().encode(self) else {
            return [:]
        }
        guard let dict = try? JSONSerialization.jsonObject(with: jsonData, options: []) as? [String: Any], let jsonObject = dict else  {
                return [:]
        }
        return jsonObject
    }

    func toJson() -> String {
        guard let jsonData = try? JSONEncoder().encode(self) else {
            return ""
        }
        guard let jsonString = String(data: jsonData, encoding: .utf8) else {
            return ""
        }
        return jsonString
    }

    static func fromJson(string: String?) -> Self? {
        return fromJson(data: string?.data(using: .utf8))
    }

    static func fromJson(data: Data?) -> Self? {
        guard let jsonData = data else {
            return nil
        }
        return try? JSONDecoder().decode(self, from: jsonData)
    }
}