c++ - 访问派生类成员的基类方法

Question

我有以下场景:

class num {
    public:
    void print(ostream* o); // Prints the n variable
};

class int_num : public num{
    public:
    int n; // Initialized by this class's constructor
};

class float_num : public num{
    public:
    float n; // Initialized by this class's constructor
};

class double_num : public num{
    public:
    double n; // Initialized by this class's constructor
};

我如何实现这样的方案

Answer 1

给它一个虚方法，在派生类型中实现:

class num {
 public:
    void print(ostream& o) const
    {  // Prints the n variable
      doPrint(o);
    }
 private:
    virtual void doPrint(ostream& os) const = 0;
};

class double_num : public num{
  public:
    double n; // Initialized by this class's constructor
 private:
  void doPrint(ostream& os) const 
  {
    os << n;
  }
};