LUMIERA.clone/tests/basics/visitingtool-test.cpp

/*
  VisitingTool(Test)  -  check the standard visitor use case

   Copyright (C)
     2008,            Hermann Vosseler <Ichthyostega@web.de>

  **Lumiera** is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; either version 2 of the License, or (at your
  option) any later version. See the file COPYING for further details.

* *****************************************************************/

/** @file visitingtool-test.cpp
 ** unit test \ref VisitingTool_test
 */


#include "lib/test/run.hpp"
#include "lib/visitor.hpp"
#include "lib/format-string.hpp"

#include <iostream>

using util::_Fmt;
using std::string;
using std::cout;


namespace lib {
namespace visitor {
namespace test1 {
  
  using VisitingTool = visitor::Tool<>;
  
  class HomoSapiens : public Visitable<>
    {
    public:
      DEFINE_PROCESSABLE_BY (VisitingTool);
    };
  
  class Boss : public HomoSapiens
    {
    public:
      DEFINE_PROCESSABLE_BY (VisitingTool);
    };
  
  class BigBoss : public Boss
    {
    public:
      DEFINE_PROCESSABLE_BY (VisitingTool);
    };
  
  class Visionary : public Boss
    {
      DEFINE_PROCESSABLE_BY (VisitingTool);
    };
  
  class Leader : public Visionary
    {
      /* can not be visited */
    };
  
  
  
  class VerboseVisitor
    : public VisitingTool
    {
    protected:
      void talk_to (string guy)
        {
          cout << _Fmt{"Hello %s, nice to meet you...\n"} % guy;
        }
    };
  
  class Babbler
    : public Applicable< Babbler
                       , Types<Boss,BigBoss,Visionary>::List   // dispatch calls to this types
                       , VerboseVisitor                       //  (base class / interface)
                       >
    {
    public:
      void treat (Boss&)    { talk_to("Boss"); }
      void treat (BigBoss&) { talk_to("Big Boss"); }
    };
  
  // note the following fine points:
  // - Babbler "forgot" to declare being applicable to HomoSapiens
  // - the class Leader hidden deep in the hierarchy is lacking an "apply()"-implementation
  
  
  
  
  /*********************************************************************//**
   * @test our lib implementation of the visitor pattern.
   *       Defines a hierarchy of test classes to check the following cases
   *       - calling the correct visiting tool specialised function
   *         for given concrete hierarchy classes
   *       - visiting tool not declaring to visit some class
   *         is silently ignored by default
   *       - newly added classes will be handled by existing
   *         functions according to inheritance relations
   */
  class VisitingTool_test : public Test
    {
      virtual void
      run (Arg)
        {
          known_visitor_known_class();
          visiting_extended_hierarchy();
        }
      
      void
      known_visitor_known_class()
        {
          Boss x1;
          BigBoss x2;
          
          // masquerade as HomoSapiens...
          HomoSapiens& homo1{x1};
          HomoSapiens& homo2{x2};
          
          cout << "=== Babbler meets Boss and BigBoss ===\n";
          Babbler bab;
          VisitingTool& vista{bab};
          homo1.apply (vista);
          homo2.apply (vista);
        }
      
      void
      visiting_extended_hierarchy()
        {
          HomoSapiens x1;
          Leader x2;
          
          HomoSapiens& homo1 (x1);
          HomoSapiens& homo2 (x2);
          
          cout << "=== Babbler meets HomoSapiens and Leader ===\n";
          Babbler bab;
          VisitingTool& vista (bab);
          homo1.apply (vista);  // silent error handler (not Applicable to HomoSapiens)
          homo2.apply (vista); //  Leader handled as Visionary and treated as Boss
        }
    };
  
  
  /** Register this test class... */
  LAUNCHER (VisitingTool_test, "unit common");
  
  
  
}}} // namespace lib::visitor::test1