Quick and dirty Swift DTO transformation layer

Transformable.swift

//
//  Transformable.swift
//  Transformable
//
//  Created by Roshan Nindrai on 10/15/18.
//  Copyright © 2018 Roshan Nindrai. All rights reserved.
//

import Foundation
import CoreData

/// Coder for decoding Resource from NSObject
struct Coder {
    static let decoder = JSONDecoder()
    static let encoder = JSONEncoder()
}

protocol Transformable: class {
    associatedtype Destination: Codable
}

protocol Transformer {
    func toDictionary() -> [AnyHashable: Any]
}

struct Transform<Source: Transformable>: Transformer {
    let source: Source
}

extension Transform {
    
    func transform<Destination: Codable>() -> Destination? where Destination == Source.Destination {
        return try? Coder.decoder.decode(Destination.self,
                                         from: JSONSerialization.data(withJSONObject: toDictionary(),
                                                                      options: .prettyPrinted))
    }
    
    func toDictionary() -> [AnyHashable: Any] {
        let mySource = Mirror(reflecting: source)
        return mySource.children.reduce(into: [AnyHashable: Any]()) { dict, property in
            if let propertyName = property.label {
                if let value = property.value as? Transformer {
                    dict.updateValue(value.toDictionary(), forKey: propertyName)
                } else {
                    dict.updateValue(property.value, forKey: propertyName)
                }
            }
        }
    }

}

struct Address: Codable {
    let street: String
    let city: String
}

struct Person: Codable {
    let name: String
    let address: Address
}

class AddressEntity: Transformable {
    typealias Destination = Address
    let street = "1333 powell st"
    let city = "Emeryville"
}


class PersonEntity: Transformable {
    typealias Destination = Person
    let name: String
    let address: Transform<AddressEntity>

    init(name: String, address: Transform<AddressEntity>) {
        self.name = name
        self.address = address
    }
}


let address = Transform(source: AddressEntity())
let person = Transform(source: PersonEntity(name: "Roshan", address: address))
print(person.transform())