---

examp17.cpp

This example is to show use of Chain Of Responsibility pattern.

1. Declare and define various handlers and requests 2. Create requets 3. Pass it to the chain head

/*
  CoreLinux++ 
  Copyright (C) 2000 CoreLinux Consortium
  
   The CoreLinux++ Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The CoreLinux++ Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  
*/   

#include <corelinux/Common.hpp>
#include <RequestHelpHandler.hpp>
#include <HandlerHelpHandler.hpp>

using namespace corelinux;

#include <iostream>
#include <exception>

//
// In module function prototypes
//

int   main( void );
void  addHelpHandler( HelpHandlerPtr );
void  callHandler( HelpRequestPtr );

//
// General Functions 
//

void  handleAssertion( AssertionCref );
void  handleException( ExceptionCref );

//
// Global data
//

//
// Main entry point
//


int main( void )
{

   cout << endl;

   //
   // Practice graceful exception management
   //


   try
   {

      // Create and register our handler types

      RequestHelpHandler   aRequestHandler;

      addHelpHandler( &aRequestHandler );

      HandlerHelpHandler   aHandlerHandler;

      addHelpHandler( &aHandlerHandler );

      // Call requests

      HelpRequest aRequestRequest( REQUEST_HELP );

      callHandler(&aRequestRequest);

      HelpRequest aHandlerRequest( HANDLER_HELP );

      callHandler(&aHandlerRequest);

      // Test the unknown

      HelpRequest aUnknownRequest( UNKNOWN_HELP );      

      callHandler(&aUnknownRequest);
   }

   catch( AssertionRef aAssert )
   {
      handleAssertion(aAssert);
   }
   catch( ExceptionRef aException )
   {
      handleException(aException);
   }
   catch( std::exception & e )
   {
      cerr  << e.what() << endl;
   }
   catch( ... )
   {
      cerr  << "Unknown exception." << endl;
   }

   return 0;               
}

// Setup the chain of responsibility root
// and perform adding to the chain

static   HelpHandlerPtr aRoot( NULLPTR );

void  addHelpHandler( HelpHandlerPtr aHandler )
{
   if( aRoot != NULLPTR )
   {
      aHandler->succeedHandler( aRoot );
   }
   else
   {
      aRoot = aHandler;
   }
}

//
// Handle the request, exception if unhandled
//

void  callHandler( HelpRequestPtr aRequest )
{
   if( aRoot != NULLPTR )
   {
      aRoot->handleRequest( aRequest );
      if( aRequest->wasHandled() == false )
      {
         cout << "Unhandled request [" << *aRequest << "] " << endl;
      }
      else
      {
         ;  // do nothing
      }
   }
   else
   {
      NEVER_GET_HERE;
   }
}

//
// Error handlers
//

void  handleAssertion( AssertionCref aAssert )
{
   cerr << aAssert.getFile() << ":" << aAssert.getLine() << ":" << 
      "Assertion: ";

   if( aAssert.getType() == Assertion::NEVERGETHERE )
   {
      cerr << "NEVER_GET_HERE";
   }
   else
   {
      if( aAssert.getType() == Assertion::REQUIRE )
      {
         cerr  << "REQUIRE";
      }
      else if( aAssert.getType() == Assertion::ENSURE )
      {
         cerr  << "ENSURE";
      }
      else if( aAssert.getType() == Assertion::CHECK )
      {
         cerr  << "CHECK";
      }
      else 
      {
         cerr  << "ASSERT";
      }
      cerr << "( " << aAssert.getWhy() << " )";
   }

   cerr << endl;
}

void  handleException( ExceptionCref aExcp )
{
   cerr << aExcp.getFile() << ":" << aExcp.getLine() << ":" <<
      "Exception: " << aExcp.getWhy() << endl;
}

/*
   Common rcs information do not modify
   $Author: prudhomm $
   $Revision: 1.2 $
   $Date: 2000/08/31 22:49:02 $
   $Locker:  $
*/

---

This is the CoreLinux++ reference manual
Provided by The CoreLinux Consortium