Greetings --
Hammad writes:
Please tell me how can base class pointer be assigned to derived
class pointer? are they both same? if they then how?
I think that the short answer to your question is to include
#include
then, if your classes are polymorphic (i.e., they have 'virtual'
methods), use 'boost::dynamic_pointer_cast'; otherwise, use
'boost::static_pointer_cast'. The dynamic casts require a vtable, but
they have the advantage of checking that a given cast is correct (that
the base pointer really is to that derived class, or some class
further down that tree of the hierarchy). A static cast simply takes
your word for it.
A longer example:
#include <iostream>
#include
#include
class base
{
public:
base() {}
};
class derived
: public base
{
public:
derived() : base() {}
special() { std::cout << "special" << std::endl; }
};
int main( int argc, char * argv [] )
{
// this is fine, since a "base *" can hold a "derived *"
boost::shared_ptr< base > bsp( new derived() );
// error! the compiler only sees the static type, and 'base' has
// no method named 'special'.
bsp->special(); // error!
// so we need to make a shared pointer with "derived" as the
// pointed-at type:
boost::shared_ptr< derived > dsp =
boost::static_pointer_cast< derived >( bsp );
// now the static type has the 'special' method:
dsp->special();
return 0;
}
