public class Message: Object, Mappable, Equatable {

    public dynamic var primaryId = ""
    public dynamic var receiver = ""
    public dynamic var sender = ""
    public dynamic var sentTime: Int64 = 0
    public dynamic var serverTime: Int64 = 0
    public dynamic var message = ""

    public required init() {
        super.init()
    }

    public required init(value: AnyObject, schema: RLMSchema) {
        super.init(value: value, schema: schema)
    }

    public required init(realm: RLMRealm, schema: RLMObjectSchema) {
        super.init(realm: realm, schema: schema)
    }

    public override static func primaryKey() -> String? {
        return "primaryId"
    }
}

public class MessageHistoryObject: Message {
   public response:Int = 0

}

let message = MessaHistoryObject()
let realm = try! Realm()
try! realm.write {
  realm.add(message)
}