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0911，类与类之间的关系，设计原则，工厂模式

news 2025/6/22 16:16:56

01_figure.cc //简单工厂

#include <math.h>
#include <iostream>
#include <string>
#include <memory>using std::cout;
using std::endl;
using std::string;
using std::unique_ptr;//-------------------------------------------------//
//-------------------------------------------------//
class Figure
{
public:virtual void display() const = 0;virtual double area() const = 0;//基类的析构函数设置为虚函数virtual ~Figure(){};
};
//-------------------------------------------------//
//-------------------------------------------------//
class Rectangle
: public Figure
{
public:Rectangle(double length = 0, double width = 0): _length(length), _width(width){cout << "Rectangle(double = 0, double = 0)" << endl;}void display() const override{cout << "Rectangle";}double area() const override{return _length * _width;}~Rectangle(){cout << "~Rectangle()" << endl;}
private:double _length;double _width;
};//-------------------------------------------------//
//-------------------------------------------------//
class Circle
: public Figure
{
public:Circle(double radius = 0): _radius(radius){cout << "Circle(double = 0)" << endl;}void display() const override{cout << "Circle";}double area() const override{return 3.14 * _radius *_radius;;}~Circle(){cout << "~Circle()" << endl;}private:double _radius;
};//-------------------------------------------------//
//-------------------------------------------------//
class Triangle
: public Figure
{
public:Triangle(double a = 0, double b = 0, double c = 0): _a(a), _b(b), _c(c){cout << "Triangle(double = 0, double = 0, double = 0)" << endl;}void display() const override{cout << "Triangle";}double area() const override{double tmp = (_a + _b + _c)/2;return sqrt(tmp * (tmp - _a) * (tmp - _b) * (tmp - _c));}~Triangle(){cout << "~Triangle()" << endl;}
private:double _a;double _b;double _c;
};
//-------------------------------------------------//
//-------------------------------------------------//
//简单工厂/静态工厂：根据产品的名字生产对应的产品
//缺点：违反 单一职责 开放闭合  依赖倒置
//           
//优点：简单  名字-->产品class Factory{
public:static Figure* create(const string & name){if(name=="triangle"){Triangle *ptri=new Triangle(10,20,20);return ptri;}else if(name=="circle"){Circle *pcir=new Circle(10);return pcir;}else if(name=="rectangle"){Rectangle *prec=new Rectangle(10.0,20.0);return prec;}else{return nullptr;}}
};
#if 0Figure* pcir=creat_c();Figure* ptri=creat_t();Figure* prec=creat_t();//读取配置文件，获取配置文件中的内容//配置文件的类型：txt,conf,xml,yang//基类接收派生类/* Rectangle *creat_r(){ */Figure *creat_r(){Rectangle *prec=new Rectangle(10,20);return prec;}Figure *creat_t(){Triangle *ptri=new Triangle(10,20,20);return ptri;}Figure *creat_c(){Circle *pcir=new Circle(10);return pcir;}
#endif//-------------------------------------------------//
//-------------------------------------------------//
void func(Figure *pfig){pfig->display();cout << "的面积 : " << pfig->area() << endl;
}//-------------------------------------------------//
//-------------------------------------------------//void test(){/* Figure * pc=Factory::create("circle"); *//* Figure * pt=Factory::create("triangle"); *//* Figure * pr=Factory::create("rectangle"); */unique_ptr<Figure> pc(Factory::create("circle"));unique_ptr<Figure> pt(Factory::create("triangle"));unique_ptr<Figure> pr(Factory::create("rectangle"));func(pc.get());func(pt.get());func(pr.get());}int main(int argc, char **argv)
{test();return 0;
}

02_figure.cc //工厂模式

#include <math.h>
#include <iostream>
#include <string>
#include <memory>using std::cout;
using std::endl;
using std::string;
using std::unique_ptr;//-------------------------------------------------//
//-------------------------------------------------//
class Figure
{
public:virtual void display() const = 0;virtual double area() const = 0;virtual ~Figure(){};
};
//-------------------------------------------------//
//-------------------------------------------------//
class Rectangle
: public Figure
{
public:Rectangle(double length = 0, double width = 0): _length(length), _width(width){cout << "Rectangle(double = 0, double = 0)" << endl;}void display() const override{cout << "Rectangle";}double area() const override{return _length * _width;}~Rectangle(){cout << "~Rectangle()" << endl;}
private:double _length;double _width;
};//-------------------------------------------------//
//-------------------------------------------------//
class Circle
: public Figure
{
public:Circle(double radius = 0): _radius(radius){cout << "Circle(double = 0)" << endl;}void display() const override{cout << "Circle";}double area() const override{return 3.14 * _radius *_radius;;}~Circle(){cout << "~Circle()" << endl;}private:double _radius;
};//-------------------------------------------------//
//-------------------------------------------------//
class Triangle
: public Figure
{
public:Triangle(double a = 0, double b = 0, double c = 0): _a(a), _b(b), _c(c){cout << "Triangle(double = 0, double = 0, double = 0)" << endl;}void display() const override{cout << "Triangle";}double area() const override{double tmp = (_a + _b + _c)/2;return sqrt(tmp * (tmp - _a) * (tmp - _b) * (tmp - _c));}~Triangle(){cout << "~Triangle()" << endl;}
private:double _a;double _b;double _c;
};
//-------------------------------------------------//
//-------------------------------------------------//
//工厂模式，为每个产品创建对应的工厂
//优点：满足 单一职责 开放闭合  依赖倒置
//缺点：工厂的数量随着产品的数量急剧上升class Factory{
public:virtual Figure* create()=0;virtual ~Factory(){}
};
class C_Factory
:public Factory
{virtual Figure* create()override{Circle *pcir=new Circle(10);return pcir;}
};
class R_Factory
:public Factory
{virtual Figure* create()override{Rectangle *pcir=new Rectangle(10,10);return pcir;}
};
class T_Factory
:public Factory
{virtual Figure* create()override{Triangle *pcir=new Triangle(3,4,5);return pcir;}
};//-------------------------------------------------//
//-------------------------------------------------//
void func(Figure *pfig){pfig->display();cout << "的面积 : " << pfig->area() << endl;
}//-------------------------------------------------//
//-------------------------------------------------//void test(){unique_ptr<Factory> recFac(new R_Factory());//创建对象unique_ptr<Figure> pr(recFac->create());//调用创建函数unique_ptr<Factory> recCir(new C_Factory());unique_ptr<Figure> pc(recCir->create());unique_ptr<Factory> recTri(new T_Factory());unique_ptr<Figure> pt(recTri->create());func(pc.get());//unique_ptr --> Figure* func(pt.get());func(pr.get());}int main(int argc, char **argv)
{test();return 0;
}

作业

01 扩展阅读（阅读，加深对面向对象的理解）
[OO真经]：https://www.cnblogs.com/leoo2sk/archive/2009/04/09/1432103.html

02 类与类之间的关系有哪几种？各自的特点怎样的？

继承/泛化关联组合聚合依赖

结构上：继承（竖向）其他（横向）

语义上：继承is，依赖use，关联/组合/聚合has

耦合程度：依赖 <关联 < 聚合< 组合<继承

代码层面：

        成员函数：依赖
        数据成员：聚合/关联（引用/指针）组合（成员子对象）
        成员函数&数据成员：继承

03 面向对象设计有哪些原则？各自的特点是什么？

单一功能，开放关闭，里氏替换，实现倒置，接口分离，迪米特，组合复用

01_ 单一功能一个类只做好一件事，只有一个引起它变化的原因
02_ 开放闭合对抽象编程，而不是对具体编程（开放实现，关闭修改
03_ 里氏替换派生类必须能替换基类（实现抽象，不能覆盖非抽象方法
04_ 接口分离设置许多小而专的借口，而不是一个大的接口
05_ 依赖倒置面向接口编程，依赖于抽象
06_ 迪米特目标是降低耦合，也叫最少知道/最少知识原则
07_ 组合复用用组合的方式替代继承

开放闭合是目标，里氏替换是基础，依赖倒置是手段