Returning derived via base pointer
Hello all. Ive been having a problem. I have a base class A and two derived classes B and C. I have a pointer to B, which I'll call E, that I want to store either A or C in, in the hopes of using just one storage location (E), as I want to store B OR C not both. It seems wasteful to have make storage for B and C when only one will be used. Also I want to be able to access data specific to these derived classes. So I've tried using a virtual function from the base which is overloaded by the derived classes to each return a pointer to themselves so I can access their data. So why does this below not work? Or even better, how can I make this work :D Thanks!
#include <iostream>
using std::cout;
class Base
{
public:
virtual Base* GetThis(){return this;}
};
class Derived: public Base
{
public:
virtual Derived* GetThis() {return this;}
void Test(){cout << "Test";}
};
int main()
{
Derived d;
Base *b = &d;
Derived *pD = b->GetThis();
return 0;
}
I get this:
error C2440: 'initializing' : cannot convert from 'Base *' to 'Derived *'
If you've read down to hear thank you for your patience! :D
#include <iostream>
using std::cout;
class Base
{
public:
virtual Base* GetThis(){return this;}
};
class Derived: public Base
{
public:
virtual Derived* GetThis() {return this;}
void Test(){cout << "Test";}
};
int main()
{
Derived d;
Base *b = &d;
Derived *pD = b->GetThis();
return 0;
}
I get this:
error C2440: 'initializing' : cannot convert from 'Base *' to 'Derived *'
If you've read down to hear thank you for your patience! :D
It seems you've found a solution, but I might suggest a rethinking of your design. If you're going to need a B object, then make a B object. When you're finished and will need a C object, delete your B object and make your C object. That way you're not wasting any memory (which appears to have been your original reason for using inheritance) and you don't have to worry about these weird type casts.
just my two cents :)
just my two cents :)
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