Abstract base class and inherited class members

[JovianGhost]

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

class AbstracBasetClass
{
};
 
class ClassA : public AbstracBasetClass
{
public:
  int numA;
};
 
class ClassB : public AbstracBasetClass
{
public:
  int numB;
};
 
class ClassC: public AbstracBasetClass
{
public:
  int numC;
};

class AbstracBasetClass
{
};

class ClassA : public AbstracBasetClass
{
public:
  int numA;
};

class ClassB : public AbstracBasetClass
{
public:
  int numB;
};

class ClassC: public AbstracBasetClass
{
public:
  int numC;
};

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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...

AbstracBasetClass* foo;
 
if (some condition)
{
  foo = new ClassA();
  foo->numA = 1;
}
else if (some other condition)
{
  foo = new ClassB();
  foo->numB = 2;
}
else if (some third condition)
{
  foo = new ClassC();
  foo->numC = 3;
}
 
// do something here with foo regardless of what its type is

AbstracBasetClass* foo;

if (some condition)
{
  foo = new ClassA();
  foo->numA = 1;
}
else if (some other condition)
{
  foo = new ClassB();
  foo->numB = 2;
}
else if (some third condition)
{
  foo = new ClassC();
  foo->numC = 3;
}

// 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

foo = new ClassA();
((ClassA*)foo)->numA = 1;

foo = new ClassA();
((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?

[aamer4yu]

Why not have a design like this -

class AbstracBasetClass
{
public:
  int number;
};
 
class ClassA : public AbstracBasetClass
{
public:
};
 
class ClassB : public AbstracBasetClass
{
public:
};
 
class ClassC: public AbstracBasetClass
{
public:
};

class AbstracBasetClass
{
public:
  int number;
};

class ClassA : public AbstracBasetClass
{
public:
};

class ClassB : public AbstracBasetClass
{
public:
};

class ClassC: public AbstracBasetClass
{
public:
};

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and then simply call foo->number = value;

or you could also do something like -

class AbstracBasetClass
{
public:
virtual void setNumber(int number) {} // empty implementation in base class
};
 
class ClassA : public AbstracBasetClass
{
public:
  int numA;
void setNumber(int number) {numA = number; } 
};
 
class ClassB : public AbstracBasetClass
{
public:
  int numB;
void setNumber(int number) {numB = number; } 
};
 
class ClassC: public AbstracBasetClass
{
public:
  int numC;
void setNumber(int number) {numC = number; } 
};

class AbstracBasetClass
{
public:
virtual void setNumber(int number) {} // empty implementation in base class
};

class ClassA : public AbstracBasetClass
{
public:
  int numA;
void setNumber(int number) {numA = number; } 
};

class ClassB : public AbstracBasetClass
{
public:
  int numB;
void setNumber(int number) {numB = number; } 
};

class ClassC: public AbstracBasetClass
{
public:
  int numC;
void setNumber(int number) {numC = number; } 
};

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then from your code you can call foo->setNumber(1);, etc depending on your if condition.

Hope some way fits you

[JovianGhost]

Thanks for the reply aamer4yu, but as I said, the member is not necessarily the same for each inherited class. ClassA for example might have bools, ClassB might have ints and floats, ClassC might have a separate object, etc. So the members of the different classes have nothing in common.

[Lykurg]

which works, but looks ugly and clunky.

But it is the "only" way. If don't want to use the casting all the time you can do it like that:

AbstracBasetClass* foo;
 
if (some condition)
{
  ClassA* classAPtr = new ClassA();
  classAPtr->numA = 1;
  foo = classAPtr;
}
 
foo->whatEver();

AbstracBasetClass* foo;

if (some condition)
{
  ClassA* classAPtr = new ClassA();
  classAPtr->numA = 1;
  foo = classAPtr;
}

foo->whatEver();

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