Question

If class inherits base class with static variable member, Will be their only one member that shared with all classes that inheritances.

I have few kinds inherits classes, and many instance of every one of them.
I want that every one of the inherits classes will have a separate static member, that shared with all of its instances.

How can it be done?

thank you, and sorry about my poor English.

edit:

class a{
static int var;};
class b::a{};
class c::a{};

Now, I want that all instances of b will have same var, and all instances of c will have same var , but the var of b will be different from the var of c.

I’m sorry again about my English, if you can correct me, please do it.

Answer 1

You can work aroud that using CRTP :

struct YourBaseBaseClass {
    // put everything that does not depend on your static variable
};

template <YourSubclass>
struct YourBaseClass : YourBaseBaseClass {
    static Member variable;
    // and everything that depend on that static variable.
};

struct AClass : YourBaseClass<AClass> {
     // there is a "variable" static variable here
};

struct AnotherClass : YourBaseClass<AnotherClass> {
     // which is different from the "variable" static variable here.
};

AClass and AnotherClass both have a variable static variable (of type Member), but the first one is a static variable from YourBaseClass<AClass> and the other is from YourBaseClass<AnotherClass>, which are two different classes.

YourBaseBaseClass is optional, but you need it if you want to manipulate AClass and AnotherClass using a YourBaseBaseClass* pointer (you cannot have a YourBaseClass* pointer, because YourBaseClass is not a class).

And remember to define those static variables.