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Full Discussion: Understand Virtual functions Internals
Top Forums Programming Understand Virtual functions Internals Post 302571761 by rupeshkp728 on Tuesday 8th of November 2011 07:52:30 AM
Old 11-08-2011
Understand Virtual functions Internals
I am just trying to understand the virtual fns. concept.

I know that if I have a virtual fn. in a base class and its overridden fn. in derived class then based upon the address of base/derived object stored in the base class pointer the fns. will be called.


In the below code I had kept the show() fn. as virtual and it used to call properly the base and derived classes show().

But when I removed the virtual tag from show() then why does not it calls derived show() inspite of base class pointer having address of derived class object?


Code:
 
class base
{
public:
    base()
    {
        printf("Base Cons\n");
    }
 
    void show()
    {
        printf("Base Show\n");
    }
};
 
class der: public base
{
public:
    der()
    {
        printf("Der Cons\n");
    }
 
    void show()
    {
        printf("Der Show\n");
    }
};
 
void yahoo(base* bpointer)
{
    printf("Address in base pointer = %u\n",bpointer);
    bpointer->show();
}
 
int _tmain(int argc, _TCHAR* argv[])
{
    class base bobj, *bptr;
    class der dobj;
 
    bptr = & bobj;
    printf("Base obj adress = %u\n",&bobj);
    yahoo(bptr);
 
    bptr = &dobj;
    printf("Base obj adress = %u\n",&dobj);
    yahoo(bptr);
 
    return 0;
}

Output of code:
Code:
Base Cons
Base Cons
Der Cons
Base obj adress = 1245027
Address in base pointer = 1245027
Base Show
Base obj adress = 1245003
Address in base pointer = 1245003
Base Show

Last edited by rupeshkp728; 11-08-2011 at 08:54 AM.. Reason: added tags around code
 

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LEARN ABOUT DEBIAN

ost_ipv6validator

ost::IPV6Validator(3)					     Library Functions Manual					     ost::IPV6Validator(3)

NAME

       ost::IPV6Validator -

       Classes derived from IPV6Address would require an specific validator to pass to the IPV6Address constructor.

SYNOPSIS

       #include <address.h>

       Inherited by ost::IPV6MulticastValidator.

   Public Member Functions
       IPV6Validator ()
	   Constructor.
       virtual ~IPV6Validator ()
	   Keeps compilers happy.
       virtual void operator() (const in6_addr address) const =0
	   Pure virtual application operator.

Detailed Description
       Classes derived from IPV6Address would require an specific validator to pass to the IPV6Address constructor.

       This is a base class for classes of function objects used by such derived classes.

       Author:
	   Federico Montesino p5087@quintero.fie.us.es Abstract base class for derived inet addresses validators.

Constructor &; Destructor Documentation
   ost::IPV6Validator::IPV6Validator () [inline]
       Constructor. Does not deal with any state.

   virtual ost::IPV6Validator::~IPV6Validator () [inline],  [virtual]
       Keeps compilers happy.

Member Function Documentation
   virtual void ost::IPV6Validator::operator() (const in6_addraddress) const [pure virtual]
       Pure virtual application operator. Apply the validation algorithm specific to derived classes.

       Implemented in ost::IPV6MulticastValidator.

Author
       Generated automatically by Doxygen for GNU CommonC++ from the source code.

GNU CommonC++							  Sat Jun 23 2012					     ost::IPV6Validator(3)
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