Question

Code:

struct A{
    const bool const_some_write_once_flag;
    A(): const_some_write_once_flag(false) { }
};
struct B: public A{
    B(): const_some_write_once_flag(true) { }
};

the error is: class ‘B’ does not have any field named ‘const_some_write_once_flag’. I believe that it’s because while being in the constructor of B, the object being created is not yet of type A, because the “inherited slice” of A has not yet been initialized.

I’ve tried several workarounds with no luck, and I’ll omit them here. Is there a way to achieve what I’m trying to do?

Answer 1

In its initializer list,B can only initialize its own data members, its direct base classes, and any virtual base classes. const_some_write_once_flag is none of these; it is a data member of A. It can only be initialized by a constructor of A.

struct A{
    const bool const_some_write_once_flag;
    A(): const_some_write_once_flag(false) { }

protected:
    A(bool flag) : const_some_write_once_flag(flag) { }
};
struct B: public A{
    B(): A(true) { }
};