How to store derived class information obtained during initialization of a base class?

Question

I have a situation when, as a side effect of data arrival to initialize the base class, the derived class calculates a part of the information that should later be available through its interface. The following gives an idea of ​​the problem using the logical information needed for the information:

class base {
public:
  base(some_initialization_data);
  // ... 
};

class derived : public base {
public:
  derived()
  : base(calc_init_data())
  {
  }

  bool condition_x_occurred() const
  {
    // How to get at the information obtained 
    // during the call to calc_init_data()? 
  }
private:
  static some_initialization_data calc_init_data()
  {
    // This piece of information will later be needed: 
    const bool condition_x_occurred = /* ... */;
    return some_initialization_data(condition_x_occurred);
  }
};

, , . . , , , 20 , undefined.

, , . , . , , , , , . , - ?

---

. , GCC 4.1.2. ++ 03 ( TR1), ++ 11.

Answer 1

++ 11, - :

class derived : public base {
public:
  derived() : derived(calc_init_data()) {}

  bool condition_x_occurred() const { return my_condition_x_occurred; }

private:
    derived(const std::pair<bool, some_initialization_data>& p) :
        base(p.second), my_condition_x_occurred(p.first)
    {}

  static std::pair<bool, some_initialization_data> calc_init_data()
  {
    // This piece of information will later be needed:
    const bool condition_x_occurred = /* ... */;
    return std::make_pair(condition_x_occurred, some_initialization_data(condition_x_occurred));
  }

private:
    bool my_condition_x_occurred;
};

++ 03 - :

class derived : public base {
public:
  static derived make_derived() { return derived(calc_init_data()); }

  bool condition_x_occurred() const { return my_condition_x_occurred; }

private:
    derived(const std::pair<bool, some_initialization_data>& p) :
        base(p.second), my_condition_x_occurred(p.first)
    {}

  static std::pair<bool, some_initialization_data> calc_init_data()
  {
    // This piece of information will later be needed:
    const bool condition_x_occurred = /* ... */;
    return std::make_pair(condition_x_occurred, some_initialization_data(condition_x_occurred));
  }

private:
    bool my_condition_x_occurred;
};

Answer 2

, :

struct derived_init
{
    bool data;
    some_initialization_data calc()
    {
        data = true;
        return some_initialization_data();
    }
};


class derived : public base {
public:
    derived()
        : derived(derived_init{})
    { }

    bool condition_x_occurred() const
    {
        return init_data.data;
    }
private:
    derived(derived_init init)
        : base(init.calc()), init_data(init)
    { }
    derived_init init_data;
};

++ 03 :

class derived : public base {
public:
    derived(derived_init init = derived_init{})
        : base(init.calc()), init_data(init)
    {
    }
private:
    derived_init init_data;
};