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Tip of the Day
Language: C++
Expertise: Beginner
May 23, 1999



Building the Right Environment to Support AI, Machine Learning and Deep Learning

Derived Classes

Functions are inherited easily. But if you have a variable in the base class and you want have the same variable but with a different type in the derived class, what to do then? for instance:
class A

class B

class Base
  A MyClass;

class Child:public Base
 B MyClass;
What happens in this case? I always encounter with pointer errors. Why?

I have never tried this, but it appears that C++ provides no support for virtual variables. Just as well, really, since virtual functions involve a lookup table, which doesn't seem like it would work very well with variables.

I really can't image why this should be a limitation, though. In general, member variables are not accessed directly. Rather, they are accessed through member functions. You should be thinking in terms of adding a new variable to your derived class and override any methods that are affected by this different variable.

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