Check for derived type (C++)

Question

How do I check at runtime if an object is of type ClassA or of derived type ClassB? In one case I have to handle both instances separately

ClassA* SomeClass:         


        

Answer 1

Use a dynamic_cast as follows:

ClassA* SomeClass::doSomething(ClassA* a)
{
    if (dynamic_cast(a)) {
        ...
    } else if (dynamic_cast(a)) {
        ...
    }
 }

dynamic_cast(ptr) will return 0 in case ptr is not a pointer of type T, and will return a pointer of type T otherwise.

dynamic_cast can usually be avoided and is an indicator of bad design / code. If you can avoid it, try to do so, as it requires RTTI in your final executable.