void* pointer to class

[sunsflower]

for example

 class A
{
     void function() {}
}

int main()
{
     void* pA = &A;
     pA->function();
     
     return 0;
}

this doesn't work. error says : expression must have pointer-to-class type. The reason I use void* is that there are many possible type of data I want to get access via the pointer. So is there a solution? thanks!

[JLBorges]

#include <iostream>

struct A
{
    virtual ~A() = default ;
    virtual void function() const { std::cout << "A::function\n" ; }
};

struct B : A
{
    virtual void function() const override { std::cout << "B::function\n" ; }
};

struct C : A
{
    virtual void function() const override { std::cout << "C::function\n" ; }
};

int main ()
{
    A a ;
    B b ;
    C c ;

    A* pa = std::addressof(a) ;
    pa->function() ;

    pa = std::addressof(b) ;
    pa->function() ;

    pa = std::addressof(c) ;
    pa->function() ;
}

https://en.wikipedia.org/wiki/Virtual_function

[sunsflower]

but what if I want this pointer to point to an integer, too?

[JLBorges]

#include <iostream>
#include <boost/any.hpp> // <std/experimental/any>

template < typename SOME_TYPE > void foo( const SOME_TYPE& reference )
{
    std::cout << "address: " << std::addressof(reference) << '\n' ;
    // do something with the object
}

template < typename SOME_TYPE > void bar( const SOME_TYPE* pointer )
{
    std::cout << "address: " << pointer << '\n' ;
    if( pointer != nullptr )
    {
       // do something with the object pointed to
    }
}


struct A {};
struct B {};

int main()
{
    const A a ;
    const B b ;
    const int i = 0 ;

    foo(a) ; bar( std::addressof(a) ) ;
    foo(b) ; bar( std::addressof(b) ) ;
    foo(i) ; bar( std::addressof(i) ) ;

    // http://www.boost.org/doc/libs/1_59_0/doc/html/any.html
    boost::any pointer = std::addressof(a) ;
    pointer = std::addressof(b) ;
    pointer = std::addressof(i) ;
}