Re: Static Class Variables, Inheritance, and Polymorphism

From:
Fei Liu <feiliu@aepnetworks.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 03 Apr 2007 17:46:26 -0400
Message-ID:
<euuhvg$5t3$1@aioe.org>
crjjrc wrote:

Hi, I've got a base class and some derived classes that look something
like this:

  class Base {
    public:
      int getType() { return type; }
    private:
      static const int type = 0;
  };

  class Derived1 : public Base {
    private:
      static const int type = 1;
  };

  class Derived2 : public Base {
    private:
      static const int type = 2;
  };

I've then got a vector declared to hold instances of Base, but it's
actually filled with various instances of Derived1 and Derived2. On
iterating through and examining each item, I'd like to be able to call
getType() and have the correct derived class's class variable
retrieved. However, I only get 0 returned. I've tried making
getType() virtual in the Base class, but that didn't help anything.

I can get this to work by defining getType() in each class to return a
literal 0, 1, or 2, but I'd think that what I'm trying do should
work. Any ideas? I don't want to dynamically cast if I can avoid it.

Thanks for any help! Let me know if I can frame the problem
differently or provide more info.

- Chris


Since you didn't post a complete code, I am guess it's most likely due
to the way you declare your vector container, as it's been explained by
other people. It's a good idea to post a compilable code that
demonstrate your problem.

Fei

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