c++ - 嵌套类变量调用

Question

我想从这个开始:

为此:

我该怎么做？子类 square 和 rectangle 的函数如何知道使用父类 shape 的变量？

我如何从 main 设置长度和宽度？

#include <iostream>
#include <cmath>
using namespace std;

class SHAPES
{
      public:
      class SQUARE
      {
            int perimeter(int length, int width)
            {
                return 4*length;
            }
            int area(int length, int width)
            {
                return length*length;
            }
      };
      public:
      class RECTANGLE
      {
            int perimeter(int length, int width)
            {
                return 2*length + 2*width;
            }
            int area(int length, int width)
            {
            return length*width;
            }
      };

};

Answer 1

我推荐其他(更好？!)格式:

class Shape
{
protected:
    int length,width;
public: 
    Shape(int l, int w): length(l), width(w){}
    int primeter() const
    {
        return (length + width) * 2;
    }
    int area() const
    {
        return length * width;
    }
};

class Rectangle : public Shape
{
public
    Rectangle(int l, int w) : Shape(l,w){}
};

class Square : public Shape
{
public:
    Square(int l): Shape(l,l){}
};


int main()
{
    Rectangle r(5,4);
    Square s(6);

    r.area();
    s.area();
}

或者使用interface with virtual function .