前言
模式介绍
在之前简单工厂模式中,我们介绍了简单工厂模式的缺陷是违背了开放-封闭原则。如果在面馆中添加了烤海参,那将会修改waiter工厂类。违背了类内封闭原则。
还以面馆为例,现在两种面,用一个服务员来卖就可以,如果这个服务员不干了,后面卖面的厨师需要兼职顶替服务员,但是厨师又不能离开灶台,就将模式改成了窗口排队式,一队海参炒面,另一队辣根汤面。每个窗口分别有一个厨师放饭,一个会做海参炒面,另一个会做辣根汤面。老板觉得这种模式挺好,万一来了一个会做烤海参的,就只需要开一个烤海参的窗口就好了,不需要重新要服务员学习,因为烤海参的就会卖。这就变成了工厂模式。
UML类图
这里涉及到2种类①我,客户端,排队买饭。②做饭厨师类,工厂类,为我生成饭。③菜品类,生成菜品类。具体关系如下UML类图:
代码实例
下面是noodle类,是为工厂类使用的,继承他就可以扩展noodle类别:
#ifndef NOODLE_H
#define NOODLE_H
class noodle
{
public:
noodle() {}
~noodle() {}
virtual void eating() = 0;
};
#endif // NOODLE_H
下面是海参炒面类,继承了noodle,实现eating方法,吃海参炒面:
#ifndef HAISHENNOODLE_H
#define HAISHENNOODLE_H
#include "noodle.h"
class haishennoodle : public noodle
{
public:
haishennoodle();
~haishennoodle();
virtual void eating();
};
#endif // HAISHENNOODLE_H
#include <iostream>
#include "haishennoodle.h"
haishennoodle::haishennoodle()
{
}
haishennoodle::~haishennoodle()
{
}
void haishennoodle::eating()
{
std::cout << "我是海参炒面,里面没有海参哦!!吃的时候注意!" << std::endl;
}
下面是辣根汤面,继承了noodle,实现eating方法,吃辣根汤面:
#ifndef LAGENNOODLE_H
#define LAGENNOODLE_H
#include "noodle.h"
class lagennoodle : public noodle
{
public:
lagennoodle();
~lagennoodle();
virtual void eating();
};
#endif // LAGENNOODLE_H
#include <iostream>
#include "lagennoodle.h"
lagennoodle::lagennoodle()
{
}
lagennoodle::~lagennoodle()
{
}
void lagennoodle::eating()
{
std::cout << "我是辣根汤面,吃完呛的哼啊!!!" << std::endl;
}
下面是waiter工厂的基类。所有工厂都继承这个类:
#ifndef WAITER_H
#define WAITER_H
class noodle;
class waiter
{
public:
waiter() {}
~waiter() {}
virtual noodle *createnoodle() = 0;
};
#endif // WAITER_H
下面是海参厨师(工厂1),海参厨师只管做海参炒面,重写了createnoodle方法:
#ifndef HAISHEN_H
#define HAISHEN_H
#include "waiter.h"
class noodle;
class haishen : public waiter
{
public:
haishen();
~haishen();
virtual noodle *createnoodle();
};
#endif // HAISHEN_H
#include <iostream>
#include "haishen.h"
#include "haishennoodle.h"
haishen::haishen()
{
}
haishen::~haishen()
{
}
noodle *haishen::createnoodle()
{
std::cout << "面是我炒得,我的名字叫海参!!!" << std::endl;
return new haishennoodle();
}
下面是辣根厨师(工厂1),辣根厨师只管做辣根汤面,重写了createnoodle方法:
#ifndef LAGEN_H
#define LAGEN_H
#include "waiter.h"
class lagen : public waiter
{
public:
lagen();
~lagen();
virtual noodle *createnoodle();
};
#endif // LAGEN_H
#include <iostream>
#include "lagen.h"
#include "lagennoodle.h"
lagen::lagen()
{
}
lagen::~lagen()
{
}
noodle *lagen::createnoodle()
{
std::cout << "吃辣根汤面,你不觉得呛得哼吗??" << std::endl;
return new lagennoodle();
}
下面是客户端,客户端通过类别,使用相应的工厂类建立相应的实例:
#include <iostream>
#include <string.h>
#include "haishen.h"
#include "lagen.h"
#include "noodle.h"
using namespace std;
char *product_list[] = {
"haishen-noodle",
"lagen-noodle",
NULL
};
int main()
{
char *p = NULL;
char *pd = "haishen-noodle";
int i = 0;
waiter *w = NULL;
noodle *n = NULL;
for(p = product_list[i]; p != NULL; i++, p = product_list[i]) {
if(strncmp(pd, p, strlen(pd)) == 0) {
if(i == 0) {
w = new haishen();
} else if(i == 1) {
w = new lagen();
} else {
cout << "对不起,请您排在队内!!!" << std::endl;
break;
}
}
}
if(w) n = w->createnoodle();
if(n) n->eating();
if(w) {
delete w; w = NULL;
}
if(n) {
delete n; n = NULL;
}
return 0;
}
下面是CMakeList.txt文件,帮助生成Makefile:
cmake_minimum_required(VERSION 2.8)
project(noodle-factory)
set(SRC_LIST main.cpp noodle.h waiter.h haishen.h haishen.cpp haishennoodle.h haishennoodle.cpp
lagennoodle.h lagennoodle.cpp lagen.h lagen.cpp)
add_executable(${PROJECT_NAME} ${SRC_LIST})
编译运行结果
代码下载链接是:https://github.com/erguangqiang/freesir_headfirst/blob/master/noodle-factory.tar.gz
使用cmake生成Makefile,并编译出可执行程序noodle。运行结果如下:
erguangqiang@elab$./noodle-factory
面是我炒得,我的名字叫海参!!!
我是海参炒面,里面没有海参哦!!吃的时候注意!
结束
工厂模式解决了简单工厂违背了的开放-封闭原则。虽然累的结构变的复杂了,但是对于扩展性得到了很大的提高。