c++ - 继承:动态派生类成员与静态派生类成员

Question

目的是实现一个基类:vector_base...

对于如何为下面概述的两个 vector 类创建基类，我有一些误解。

首先:基类是否应该为每个派生类都有一个构造函数和一个默认构造函数？或者有没有办法在这种情况下调用基础构造函数来完成派生......

class three: public two
{
  private:

    double z;

  public:

    three(double x = 0, double y = 0, double z = 0)
      : two(x, y), // call two(double, double) to initialize x & y
      z(z)

    // ...
};

第二:基类应该有两组坐标(x，y，z)静态还是动态(指针类型)？

第三:访问器和修改器在每种情况下如何工作；是否有任何理由考虑关键字:virtual 和 override？

基本上我不明白如果数据成员是double类型和double*类型如何实现多态

class vector_static 
{
  private:
    double x;
    double y;
    double z;

  public:

    vector_static(double x = 0, double y = 0, double z = 0)
      : x(x), y(y), z(z) {}
    vector_static(const vector_static& copy)
      : x(copy.x), y(copy.y), z(copy.z) {}

    ~vector_static() 
    { 
      std::cout << "vector_static::~vector_static() " << std::endl; 
};

class vector_dynamic
{
  private:
    double* x = nullptr;
    double* y = nullptr;
    double* z = nullptr;

  public:

    vector_dynamic(double x = 0, double y = 0, double z = 0)
      : x {new double (x)},
      y {new double (y)},
      z {new double (z)}
    {
    }

    vector_dynamic(const vector_dynamic& copy)
      : x{new double (copy.get_x() )},
      y{new double (copy.get_y() )},
      z{new double (copy.get_z() )}
    {
    }

    ~vector_dynamic()
    {
      std::cout << "\nvector_dynamic::~vector_dynamic()" << std::endl;
      delete x;
      delete y;
      delete z;
    }
};

Answer 1

vector_static 和 vector_dynamic 没有关系，你不能多态地使用它们。他们需要有一个共同的基类来定义可以调用以访问坐标的虚函数。然后您将覆盖每个派生类中的那些方法以获取或设置坐标；一个将直接访问成员，另一个将取消引用指针。

class vector_generic {
public:
    virtual double getX();
    virtual void setX(double);
    ...
}

class vector_static : public vector_generic {
public:
    double getX() {
        return x;
    }
    double setX(double newX) {
        x = newX;
    }
    ...
}

class vector_dynamic : public vector_generic {
public:
    double getX() {
        return *x;
    }
    double setX(double newX) {
        *x = newX;
    }
    ...
}

有了这个，你就可以做:

vector_generic *vec1 = new vector_static();
vector_generic *vec2 = new vector_dynamic();
cout << vec1->getX() << vec2->getX() << '\n';