一，设计模式简介

强调了抽象的概念，而不是分而治之，上代码

#include <iostream>
#include <vector>

class Shape
{
public:
? ? virtual void draw() = 0;
? ? virtual ~Shape() {}
};

class Point : public Shape
{
public:
? ? Point()
? ? {

? ? }
? ? ~Point()
? ? {

? ? }
? ? virtual void draw()
? ? {
? ? ? ? std::cout << "use Point" << std::endl;
? ? }
};

class Line : public Shape?
{
public:
? ? Line()
? ? {
?
? ? }
? ? ~Line()
? ? {

? ? }

? ? virtual void draw()
? ? {
? ? ? ? std::cout << "use line" << std::endl;
? ? }
};

class Rect : public Shape
{
public:

? ? Rect()
? ? {

? ? }
? ? ~Rect()
? ? {

? ? }

? ? virtual void draw()
? ? {
? ? ? ? std::cout << "use Rect" << std::endl;
? ? }

};

int main()
{
? ? Shape* ptShape = new Point;?
? ? Shape* lineShape = new Line;
? ? Shape* rectShape = new Rect;

? ? std::vector<Shape*> shapeVector; //这里Shape要用指针,多态性
? ? shapeVector.push_back(ptShape);
? ? shapeVector.push_back(lineShape);
? ? shapeVector.push_back(rectShape);
? ? for (auto& theShape : shapeVector) ?//针对各种形状，各负其责
? ? {
? ? ? ? theShape->draw();
? ? }

? ??
? ? delete ptShape;
? ? ptShape = nullptr;
? ? delete lineShape;
? ? lineShape = nullptr;
? ? delete rectShape;
? ? rectShape = nullptr;

? ? return 0;
}

?

打印结果是:

use Point
use line
use Rect

?

这里用了抽象类，

如果分而治之，则会需要3个数组，分别判断具体属于哪个类，是点，圆还是线，再调用相应类的方法。如果再添加，还需要再加数组，1万个种类的图形则需要1万种数组