command.h

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//////////////////////////////////////////////////////////////////////
// 6/25/02      Aaron Lefohn    Scientific Computing and Imaging Institute
// School of Computing          University of Utah
//
//  This library is free software; you can redistribute it and/or
//  modify it under the terms of the GNU Lesser General Public
//  License as published by the Free Software Foundation; either
//  version 2.1 of the License, or (at your option) any later version.
//
//  This library 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
//  Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public
//  License along with this library; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

#ifndef _GLIFT_COMMAND_H_
#define _GLIFT_COMMAND_H_

#include "gliftDecl.h"

namespace glift {

   /// Typdefs
typedef void (*VoidFuncPtr)(); /// A Ptr to a non-member func. that takes no args and returns no value.

/////////////////////////////////////////////////////////////////////////
///
/// command.h - A simple "Command" object that allows for 'void name()' member
///             callbacks.
/// 
/// - Taken from pp. 239-241 of "Design Patterns: Elements of \n 
///   Reusable Object-Oriented Software" by Gamma, Helm, Johnson, and Vlissides. \n 
///   Copywrite 1995, Addison Wessley.
/// - To make class that takes either a C-style function pointer or a \n
///   pointer-to-member (PTM), have it take a Command* and either instantiate a \n 
///   "Command0" or a "MemberCommand0".
/// - Instantiate 'MemberCommand0' with an instance of the class containing \n
///   the callback method and a pointer to the callback name.
///   
///   Example:
/// \code
///     AClass a;
///     MemberCommand0<AClass>* callback = new MemberCommand0(&a, &AClass::daCallBack);
///     callback->execute();    //Calls a.daCallBack() 
/// \endcode
///
/// Command - Base class
//////////////////////////
class _export_ Command
{
public:
   virtual ~Command();
   virtual void execute() = 0;
   virtual Command* clone() = 0;

protected:
   Command() {}

};

//////////////////////////
/// Command0 - Base class
//////////////////////////
class _export_ Command0 : public Command
{
public:
   typedef void (*Action) ();

   Command0( Action a );

   virtual void execute() {m_action();}
   virtual Command* clone();

private:
   Action m_action;
};

///////////////////////////////
/// MemberCommand0 - Base class
///////////////////////////////
template <class Receiver>
class _export_ MemberCommand0 : public Command
{
public:
   typedef void (Receiver::* Action) ();

   MemberCommand0(  Receiver* r, Action a );

   virtual void execute();
   virtual Command* clone();

private:
   Receiver* m_receiver;
   Action                       m_action;
};

template <class Receiver>
MemberCommand0<Receiver>::MemberCommand0(  Receiver* r, Action a )
: m_receiver(r), 
m_action(a) 
{}

template <class Receiver>
void MemberCommand0<Receiver>::execute() {
   (m_receiver->*m_action)();
}

template <class Receiver>
Command* MemberCommand0<Receiver>::clone()
{
   return new MemberCommand0<Receiver>(*this);
}

} /// End of namespace glift

#endif

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