Swift deserialization

Entity.swift

infix operator <<<

class Entity : CustomDebugStringConvertible {
    
    static func <<<(_ image: Entity, assignment: (ReferenceWritableKeyPath<Entity, String?>, key: Entity.Keys, source: [String : Any])) {
        let keypath = assignment.0
        let value = assignment.source[assignment.key.rawValue]
        if value != nil {
            image[keyPath: keypath] = String(describing: value!)
        } else {
            image[keyPath: keypath] = nil
        }
    }
    
    enum Keys : String, CaseIterable {
        case keyA = "keyA"
        case keyB = "keyB"
        case keyC = "keyC"
        case keyD = "keyD"
        
        var keyPath: ReferenceWritableKeyPath<Entity, String?> {
            switch self {
                case .keyA: return \Entity.keyA
                case .keyB: return \Entity.keyB
                case .keyC: return \Entity.keyC
                case .keyD: return \Entity.keyD
            }
        }
    }
    
    private var keyA : String?
    private var keyB : String?
    private var keyC : String?
    private var keyD : String?
    
    init(dictionary: [String : Any]) {
        
        for cs in Keys.allCases {
            self <<< (cs.keyPath, key: cs, dictionary)
        }
    }
    
    var debugDescription: String {
        var retVal : String = ""
        for cs in Keys.allCases {
            retVal.append("\(self[keyPath: cs.keyPath])\n")
        }
        return retVal
    }
}

let entity = Entity(dictionary: [ "keyA" : "1", "keyB" : "2", "keyC" : "3", "keyD" : "4"  ])
print(entity)