pClass1 = (Class1*)pBase->next without (Class1*) cast

Question

Hi, i have

class Base
{
   Base* next;
}

class Class1 : Base
{
}

Base* pBase = new Base();
Class1* pTest = new Class1();
pBase->next = pTest;

Class1* pClass1;
pClass1 = (Class1*)pBase->next;

I want to be able to write

pClass1 = pBase->next;

and get no compilation error C2440 (cannot convert). Or in other words I want pClass1 point to a class that pBase->next points to.

Is it possible with some operator overloading? How to do it?

Answer 1

If - at development time - you're sure that next points to an instance of Class1, make next a Class1 pointer instead of a Base pointer.

If you're not sure, and you only know it at compile time, you have to use a dynamic cast (possibly next will point to a Class2 instance later).

Answer 2

The closest I can get to what you are after is this:

class Class1;

class Base
{
public:
    Base* next;

    operator Class1*()
    {
        return (Class1*)this;
    }
};

class Class1 : public Base
{
};

and:

Base* pBase = new Base();
Class1* pTest = new Class1();
pBase->next     = pTest;

Class1* pClass1;
pClass1 = *pBase->next;

But this is really messing around with C++ in ways that you will pay for severely later. Just use one of the casts mentioned by Patrick.

Answer 3

template<class T>
class Base 
{ 
   T* next; 
} 

class Class1 : Base<Class1> 
{ 
} 

Class1* pTest1 = new Class1(); 
Class1* pTest2 = new Class1(); 
pTest1->next = pTest2;

Class1* pClass1; 
pClass1 = pTest1->next;