text: //
  // Created by Hai Nguyen on 2018-12-17.
  // Copyright (c) 2018 Hai Nguyen. All rights reserved.
  //
  
  #import <Foundation/Foundation.h>
  
  @class User;
  
  @protocol AuthenticationObserver <NSObject>
  @required
  - (void)onChange:(User *) user;
  @end
  
  @protocol BroadcastService <NSObject>
  @required
  - (void)subscribeOnAuthentication:(NSObject <AuthenticationObserver>*)subscriber;
  @end