UserDefinedExceptions.cpp

#include <vcl.h>
#include <iostream.h>
#pragma hdrstop

#include "UserDefinedExceptions.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------

//Global variable
bool Throw;

__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
    Throw  = false;
}
//---------------------------------------------------------------------------

class DivisionError
{
  private:

  public:
     //CONSTRUCTOR
     DivisionError()
     {
     }

     void Response();      //Response function
};
//--------------------------------------------------------------------

void DivisionError::Response()
{
    //Respond to the user defined exception by displayoing an error
    //message and terminating the program.
    ShowMessage("DivisionError Response(): Attempt to divide by 0");
    Application->Terminate();
}
//--------------------------------------------------------------------

class Division
{
  private:
     double numerator;
     double denominator;

  public:
     Division ( double n, double d ); //CONSTRUCTOR WITH TWO ARGUMENTS
     double DoDivision();             //Method to perform the division
};
//--------------------------------------------------------------------

Division::Division ( double n, double d )
{
//Division Constructor with two arguments

// Exceptions shouh be thrown from the
// Division Constructor to centralize Error
// Detection

    if ( d == 0 )
    {
        DivisionError DivisionError;
        //"throw user defined exception"
        Throw = true;
    }
    numerator   = n;
    denominator = d;
}
//----------------------------------------------------------------------

double Division::DoDivision()
{
    if ( Throw )
    {
        return 0;
    }
    else
    {
        return numerator/denominator;
    }
}
//--------------------------------------------------------------------

void DisplayDivision( Division D )
{
    //The argument to this function is a Division object

    //Show the result of the division in a Box only
    //if user defined exception was not generated.
    if ( !Throw )
    {
        ShowMessage( FloatToStr( D.DoDivision() ) );
    }
}
//--------------------------------------------------------------------

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    try
    {
        Division Division1( 100, 10 ); //Create an object Division1
        DisplayDivision( Division1 );
        Division Division2( 100, 5 );  //Create an object Division2
        DisplayDivision( Division2 );

        //Division by zero
        Division Division3( 100,  0 ); //Create an object Division1
        DisplayDivision( Division3 );
    }
    catch ( ... )
    {
        //Place the desired response code for the
        //compiler generated exceptions here
    }

    //"USER DEFINED CATCH"
    if ( Throw )
    {
       //ShowMessage("Throw");
       DivisionError Error;
       Error.Response();
    }
}

UserDefinedExceptions.h

#ifndef UserDefinedExceptionsH
#define UserDefinedExceptionsH
//---------------------------------------------------------------------------
#include <Classes.hpp>
#include <Controls.hpp>
#include <StdCtrls.hpp>
#include <Forms.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE-managed Components
        TButton *Button1;
        void __fastcall Button1Click(TObject *Sender);
private:	// User declarations
public:		// User declarations
        __fastcall TForm1(TComponent* Owner);

};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif