参考： 设计模式笔记

简单工厂模式

● 将类的创建过程交给工厂类实现，如果需要一个类对象，则直接通过工厂创建一个类。
● 简单工厂模式不符合开闭原则
● 适用场景：工厂类负责创建的对象比较少；客户端只知道传入工厂类的参数，对于如何创建对象不关心

/*
类的创建过程交给工厂类来实现，如果需要一个类的对象，则直接通过工厂创建一个对应的类对象
*/
#include<iostream>
using namespace std;
class AbstractFruit{
public:virtual void showName()=0;
};//苹果
class Apple:public AbstractFruit{
public:virtual void showName(){cout<<"i am a appple"<<endl;}
};
//香蕉
class Banana:public AbstractFruit{
public:virtual void showName(){cout<<"i am a banana"<<endl;}
};//水果工厂
class FruitFactory{
public:static AbstractFruit*createFruit(string type){if(type=="apple"){return new Apple();}else if(type=="banana"){return new Banana();}else return nullptr;}
};int main(){FruitFactory*factory=new FruitFactory();AbstractFruit*fruit=factory->createFruit("apple");fruit->showName();//i am a apppledelete fruit;fruit=factory->createFruit("banana");fruit->showName();//i am a bananadelete fruit;delete factory;return 0;}

工厂模式（简单工厂模式+开闭原则）

● 代码扩展时不需要修改工厂类
● 类急速膨胀，不利于维护
● 适用场景：消费者不关心它所要创建的产品类；或者知道要创建的产品类二不关心如何创建的时候

/*简单工厂模式+开闭原则
*/
#include<iostream>
using namespace std;
class AbstractFruit{
public:virtual void showname()=0;
};class Apple:public AbstractFruit{
public:virtual void showname(){cout<<"i am a apple"<<endl;}
};class Banana:public AbstractFruit{
public:virtual void showname(){cout<<"i am a banana"<<endl;}
};
class Orange:public AbstractFruit{
public:virtual void showname(){cout<<"i am an orange"<<endl;}
};//之前是水果工厂，如果要添加对象都会在工厂里面添加，破坏了开闭原则
//设计成抽象工厂
class AbstractFactory{
public:virtual AbstractFruit*createFruit()=0;};//苹果工厂
class AppleFactory:public AbstractFactory{
public:virtual AbstractFruit*createFruit(){return new Apple();}
};//香蕉工厂
class BananaFactory:public AbstractFactory{
public:virtual AbstractFruit*createFruit(){return new Banana();}
};
//橙子工厂
class OrangeFactory:public AbstractFactory{
public:virtual AbstractFruit*createFruit(){return new Orange();}
};int main(){AbstractFactory*factory=new AppleFactory();AbstractFruit*fruit=factory->createFruit();fruit->showname();//i am a appledelete factory;delete fruit;factory=new BananaFactory();fruit=factory->createFruit();fruit->showname(); //i am a bananadelete factory;delete fruit;factory=new OrangeFactory();fruit=factory->createFruit();fruit->showname();//i am an orangedelete factory;delete fruit;return 0;}

抽象工厂模式（增加产品族方便）

● 产品族：同一产地或者同一产商，功能不同
● 产品等级：功能相同，产地或者产商不同
● 不符合开闭原则，增加新的产品等级麻烦，甚至要在抽象层修改代码
● 适用场景：

1. 系统中有多于一个的产品族。而每次只使用其中某一产品族。可以通过配置文件等方式来使得用户可以动态改变产品族，也可以很方便地增加新的产品族。
2. 产品等级结构稳定。设计完成之后，不会向系统中增加新的产品等级结构或者删除已有的产品等级结构。

/*针对产品族而不是产品等级结构
*/
#include<iostream>
using namespace std;
//抽象产品等级
class AbstractApple{
public:virtual void showname()=0;
};
class AbstractBanana{
public:virtual void showname()=0;
};
//具体产品等级
//武汉苹果
class AppleFromWhuhan:public AbstractApple{
public:virtual void showname(){cout<<" apple frome whuhan"<<endl;}
};
//上海苹果
class AppleFromShanghai:public AbstractApple{
public:virtual void showname(){cout<<" apple frome shanghai"<<endl;}
};
//武汉香蕉
class BananaFromWhuhan:public AbstractBanana{
public:virtual void showname(){cout<<" banana frome whuhan"<<endl;}
};
//上海香蕉
class BananafromShanghai:public AbstractBanana{
public:virtual void showname(){cout<<"banana frome shanghai"<<endl;}
};
//抽象工厂
class AbstractFactory{
public :virtual AbstractApple*createApple()=0;virtual AbstractBanana*createBanana()=0;};
//武汉工厂
class WhuhanFactory:public AbstractFactory{
public:AbstractApple*createApple(){return new AppleFromWhuhan();}AbstractBanana*createBanana(){return new BananaFromWhuhan();}
};
//上海工厂
class ShanghaiFactory:public AbstractFactory{
public:AbstractApple*createApple(){return new AppleFromShanghai();}AbstractBanana*createBanana(){return new BananafromShanghai();}
};int main(){AbstractFactory*factory=nullptr;AbstractApple*apple=nullptr;AbstractBanana*banana=nullptr;//武汉苹果和香蕉factory=new WhuhanFactory();apple=factory->createApple();banana=factory->createBanana();apple->showname();// apple frome whuhanbanana->showname();// banana frome whuhandelete factory;delete apple;delete banana;//上海苹果和香蕉factory=new ShanghaiFactory();apple=factory->createApple();banana=factory->createBanana();apple->showname();// apple frome shanghaibanana->showname();//banana frome shanghaidelete factory;delete apple;delete banana;
}