Ichthyostega
09e7e1f8f5
Actually I arried at the conclusion, that the *receiving* of a diff representation is actually a typical double-dispatch situation. This leads to the attempt to come up with a specialised visitor as standard pattern to handle and apply a diff. Obviously, we do not want the classical GoF-Visitor, but (yes, we had that discussion allready) -- well in terms of runtime cost, we have to deal with at least two indirections anyway; so now I'm exploring the idea to implement one of these indirections through a functor object, which at the same time acts as "Tag" in the diff representation language (instead of using an enum as tag)
158 lines
4.1 KiB
C++
158 lines
4.1 KiB
C++
/*
|
|
VisitingTool(Test) - check the standard visitor use case
|
|
|
|
Copyright (C) Lumiera.org
|
|
2008, Hermann Vosseler <Ichthyostega@web.de>
|
|
|
|
This program 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.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program; if not, write to the Free Software
|
|
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
|
|
|
* *****************************************************/
|
|
|
|
|
|
#include "lib/test/run.hpp"
|
|
#include "lib/visitor.hpp"
|
|
|
|
#include <boost/format.hpp>
|
|
#include <iostream>
|
|
|
|
using boost::format;
|
|
using std::string;
|
|
using std::cout;
|
|
|
|
|
|
namespace lib {
|
|
namespace visitor {
|
|
namespace test1 {
|
|
|
|
typedef visitor::Tool<> VisitingTool;
|
|
|
|
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
|
|
{
|
|
};
|
|
|
|
|
|
|
|
class VerboseVisitor
|
|
: public VisitingTool
|
|
{
|
|
protected:
|
|
void talk_to (string guy)
|
|
{
|
|
cout << format ("Hello %s, nice to meet you...\n") % guy;
|
|
}
|
|
};
|
|
|
|
class Babbler
|
|
: public Applicable< Babbler
|
|
, Types<Boss,BigBoss,Visionary>::List // dispatch calls to this types
|
|
, VerboseVisitor
|
|
>
|
|
{
|
|
public:
|
|
void treat (Boss&) { talk_to("Boss"); }
|
|
void treat (BigBoss&) { talk_to("Big Boss"); }
|
|
};
|
|
|
|
// note the following details:
|
|
// - Babbler "forgot" to declare being applicable to HomoSapiens
|
|
// - we have new derived class Leader without separate "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
|