【设计模式】工厂模式

---

一、工厂模式

工厂模式是对简单工厂模式的优化，以汽车为例，工厂模式有以下角色

• 抽象工厂类：抽象汽车工厂
• 具体工厂类：轿车工厂类、公交工厂类
• 抽象产品类：汽车产品类
• 具体产品类：汽车、公交

各类关系图：

二、工厂模式的实现

Factory.h

#ifndef FACTORY_H
#define FACTORY_H
#include <iostream>
#include <string>

using namespace std;
//抽象产品类
class Products
{
public:
	//产品方法
	virtual void productMethod() = 0;
};
//car产品类
class car : public Products
{
public:
	void productMethod()
	{
		cout << " car " << endl;
	}
};

//bus产品类
class bus : public Products
{
public:
	void productMethod()
	{
		cout << " bus " << endl;
	}
};


//抽象工厂类
class BaseFactory
{
public:
	virtual Products* create() = 0;
};

//car工厂类
class carFactory : public BaseFactory
{
public:
	Products* create()
	{
		return new car();
	}
};

//bus工厂类
class busFactory : public BaseFactory
{
public:
	Products* create()
	{
		return new bus();
	}
};

#endif

client.h

#include "Factory.h"

int main()
{
	/*
	使用流程:
	1. 需要什么产品
	2. 构建对应工厂
	3. 使用对应工厂生产对应产品
	4. 使用产品对应方法
	*/

	//生产小轿车
	BaseFactory* bf = new carFactory();
	Products* bp = bf->create();
	bp->productMethod();
	
	delete bf;
	delete bp;


	//生产公交车
	bf = new busFactory();
	bp = bf->create();
	bp->productMethod();

	delete bf;
	delete bp;
	return 0;
}

---

三、unique_ptr的优化

Factory.h

#ifndef FACTORY_H
#define FACTORY_H
#include <iostream>
#include <string>
#include <memory>
using namespace std;
//抽象产品类
class Products
{
public:
	//产品方法
	virtual void productMethod() = 0;
};
//car产品类
class car : public Products
{
public:
	void productMethod()
	{
		cout << " car " << endl;
	}
};

//bus产品类
class bus : public Products
{
public:
	void productMethod()
	{
		cout << " bus " << endl;
	}
};


//抽象工厂类
class BaseFactory
{
public:
	virtual unique_ptr<Products> create() = 0;
};

//car工厂类
class carFactory : public BaseFactory
{
public:
	unique_ptr<Products> create()
	{
		return unique_ptr<Products>(new car());
	}
};

//bus工厂类
class busFactory : public BaseFactory
{
public:
	unique_ptr<Products> create()
	{
		return unique_ptr<Products>(new bus());
	}
};

#endif

client.h

//工厂模式客户端
#include "Factory.h"

int main()
{
	//生产小轿车
	unique_ptr<BaseFactory> bf(new carFactory());
	unique_ptr<Products> bp = bf->create();
	bp->productMethod();

	//生产公交车
	bf.reset(new busFactory());
	bp = bf->create();
	bp->productMethod();

	return 0;
}