Re: Problem type-casting to a derived class
Rui Maciel <rui.maciel@gmail.com> writes:
Consider that I have the following classes: Base, A, B, Derived
Class A inherits class Base and class Derived inherits both class A
and class B. So, the inheritance diagram would be something like
(mind the ASCII art)
Base
|
A B
-------
|
Derived
Let's assume that I get a pointer to an object of type Base. Yet, I
need to access attributes which are defined in class B.
The thing is, a dynamic_cast<> from Base to B fails to materialize and
a reinterpret_cast<> also appears to fail.
In what way does the dynamic_cast<B*> fail?
So, is this possible? If so, what's the secret?
10:23:05 Paul Bibbings@JIJOU
/cygdrive/d/CPPProjects/CLCPP $cat casting_to_derived.cpp // file: casting_to_derived.cpp
#include <cassert>
class Base {
public:
virtual ~Base() { }
};
class A : public Base { };
class B { };
class Derived : public A, public B { };
int main()
{
Derived d;
Base *b_ptr = &d;
assert(dynamic_cast<B*>(b_ptr));
}
10:23:10 Paul Bibbings@JIJOU
/cygdrive/d/CPPProjects/CLCPP $g++ -static -o casting_to_derived
casting_to_derived.cpp
10:23:15 Paul Bibbings@JIJOU
/cygdrive/d/CPPProjects/CLCPP $./casting_to_derived
10:23:23 Paul Bibbings@JIJOU
/cygdrive/d/CPPProjects/CLCPP $
Regards
Paul Bibbings
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