Can my class know/handle casting?

With assignment and copying you can implement an operator to handle those operations ina custom manner. Is it possible to do the same for casting of pointers? I know that in casting objects I can simply make a constructor that takes the Base type and it'll handle it, but what about pointers?

Code:

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class A
{
    virtual void foo() {}
};

class B : public A
{
};

int main()
{
    A* a;
    B* b;

    //Is there a way to write a function in A that will be called when i do either of these?
    b = ( B* ) a;
    b = dynamic_cast<B*> a;
}

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Why not just have class A have a virtual copy() function and the equal operator. Then the equal operator will always call the copy() for the most recently defined version of copy().

Quote:

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Originally Posted by master5001

Why not just have class A have a virtual copy() function and the equal operator. Then the equal operator will always call the copy() for the most recently defined version of copy().

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The only problem with that is it doesn't handle this case:

Code:

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B* b =  new B();

( ( A* ) b )->SomeMethod();

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If you need that case then I would imagine something is seriously wrong with your design. As usual, what are you trying to do?

You can overload a conversion. You can not overload a cast.

Ah yes, of course. I misunderstood what you wanted. I betcha can't name a language that does work like that.

it will work if

A *a = new B();

Actually, you can overload a cast. But you can't overload anything for types you didn't define, and pointers all count as built-in types.

Quote:

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Originally Posted by m37h0d

it will work if

A *a = new B();

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this apparently is not true if B inherits virtually from A

Quote:

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this apparently is not true if B inherits virtually from A

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No, it is still true, as long as public inheritance is used. Of course, in the above code foo() is a private member function.

Quote:

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Originally Posted by CornedBee

Actually, you can overload a cast. But you can't overload anything for types you didn't define, and pointers all count as built-in types.

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You can overload dynamic_cast<>, static_cast<>, or const_cast<>? That's what I mean by "cast."

Expressions like (Type1)obj2 are often said to be "casting" obj2 to Type1, but I tend to call it a conversion, not a cast.

Quote:

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Expressions like (Type1)obj2 are often said to be "casting" obj2 to Type1, but I tend to call it a conversion, not a cast.

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Yeah, the C++ Standard calls them conversion functions too.

I meant you can overload the conversion abilities, indeed. You can't overload the four cast operators, which, by the way, is a pity.