| Factory
Method:(1)、意图：定义一个用于创建对象的接口，让子类决定实例化哪一个类。Factory Method使一个类的实例化延迟到其子类；(2)、适用性：当一个类不知道它所必须创建的对象的类的时候；当一个类希望由它的子类来指定它所创建的对象的时候；当类将创建对象的职责委托给多个帮助子类中的某一个，并且你希望将哪一个帮助子类是代理者这一信息局部化的时候。
示例代码1：
#include <string>
#include <iostream>
using namespace std;
//实例基类，相当于Product（为了方便，没用抽象）
class LeiFeng
{
public:
virtual void Sweep()
{
cout<<"雷锋扫地"<<endl;
}
};
//学雷锋的大学生相当于ConcreteProduct
class Student : public LeiFeng
{
public:
virtual void Sweep()
{
cout<<"大学生扫地"<<endl;
}
};
//学雷锋的志愿者，相当于ConcreteProduct
class Volenter : public LeiFeng
{
public:
virtual void Sweep()
{
cout<<"志愿者扫地"<<endl;
}
};
//工厂基类 Creator
class LeiFangFactory
{
public:
virtual LeiFeng* CreateLeiFeng()
{
return new LeiFeng();
}
};
//工厂具体类
class StudentFactory : public LeiFangFactory
{
public:
virtual LeiFeng* CreateLeiFeng()
{
return new Student();
}
};
class VolenterFactory : public LeiFangFactory
{
public:
virtual LeiFeng* CreateLeiFeng()
{
return new Volenter();
}
};
//客户端
int main()
{
LeiFangFactory* sf = new LeiFangFactory();
LeiFeng *s = sf->CreateLeiFeng();
s->Sweep();
delete s;
delete sf;
/*result:
雷锋扫地
*/
return 0;
} |
示例代码2：
product.h：
#ifndef _PRODUCT_H_
#define _PRODUCT_H_
class Product
{
public:
virtual ~Product() = 0;
protected:
Product();
private:
};
class ConcreteProduct : public Product
{
public:
~ConcreteProduct();
ConcreteProduct();
protected:
private:
};
#endif// ~_PRODUCT_H_ |
product.cpp：
#include "product.h"
#include <iostream>
using namespace std;
Product::Product()
{
}
Product::~Product()
{
}
ConcreteProduct::ConcreteProduct()
{
cout<<"ConcreteProduct ..."<<endl;
}
ConcreteProduct::~ConcreteProduct()
{
} |
factory.h：
#ifndef _FACTORY_H_
#define _FACTORY_H_
class Product;
class Factory
{
public:
virtual ~Factory() = 0;
virtual Product* CreateProduct() = 0;
protected:
Factory();
private:
};
class ConcreteFactory : public Factory
{
public:
~ConcreteFactory();
ConcreteFactory();
Product* CreateProduct();
protected:
private:
};
#endif//~_FACTORY_H_ |
factory.cpp：
#include "factory.h"
#include "product.h"
#include <iostream>
using namespace std;
Factory::Factory()
{
}
Factory::~Factory()
{
}
ConcreteFactory::ConcreteFactory()
{
cout<<"ConcreteFactory ..."<<endl;
}
ConcreteFactory::~ConcreteFactory()
{
}
Product* ConcreteFactory::CreateProduct()
{
return new ConcreteProduct();
} |
main.cpp：
#include "factory.h"
#include "product.h"
#include <iostream>
using namespace std;
int main()
{
Factory* fac = new ConcreteFactory();
Product* p = fac->CreateProduct();
/*result:
ConcreteFactory ...
ConcreteProduct ...
*/
return 0;
} |
工厂方法模式结构图：
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