I've got an abstract base with extremely minimal functionality, and several classes that inherit it. So for example...

Qt Code: 
  1. class AbstracBasetClass
  2. {
  3. };
  4.  
  5. class ClassA : public AbstracBasetClass
  6. {
  7. public:
  8.   int numA;
  9. };
  10.  
  11. class ClassB : public AbstracBasetClass
  12. {
  13. public:
  14.   int numB;
  15. };
  16.  
  17. class ClassC: public AbstracBasetClass
  18. {
  19. public:
  20.   int numC;
  21. };
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For the sake of simplicity each of the members is an int, but in my implementation they may be completely different and unrelated.

Now in my code, I have to instantiate one of these inherited classes and access the members, then do something with the class. So, I'll have something like this...

Qt Code: 
  1. AbstracBasetClass* foo;
  2.  
  3. if (some condition)
  4. {
  5.   foo = new ClassA();
  6.   foo->numA = 1;
  7. }
  8. else if (some other condition)
  9. {
  10.   foo = new ClassB();
  11.   foo->numB = 2;
  12. }
  13. else if (some third condition)
  14. {
  15.   foo = new ClassC();
  16.   foo->numC = 3;
  17. }
  18.  
  19. // do something here with foo regardless of what its type is
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Now this is perfectly valid of course, since foo is a pointer to the abstract base class and I'm merely instantiating one of the inherited classes. The problem is when I try to access the member, the compiler complains that "class AbstractBaseClass has no member named" and the member name in question. So instead, I have to do something like

Qt Code: 
  1. foo = new ClassA();
  2. ((ClassA*)foo)->numA = 1;
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which works, but looks ugly and clunky.
I could just declare foo within each if block, but then the part at the end where I "do something with foo" fails, because the compiler says that foo isn't defined.

I'm wondering if there's any way around this, or is this it?