文章目录
-
- 1. 什么是简单工厂模式?
- 2. 简单工厂模式的适用场景?
-
- 2.1 优点
- 2.2 缺点
- 3. 怎样使用简单工厂模式?
-
- 3.1 方法
- 3.2 UML类图
- 4. 实例
-
- 4.1 结果(结论先行)
- 4.2 具体实现
-
- 4.2.1 简单工厂的静态接口
- 4.2.2 四则运算符继承体系代码
1. 什么是简单工厂模式?
当出现批量化的产品时,使用单独的类创建每个产品,实现去实例化对象。
2. 简单工厂模式的适用场景?
优缺点有参考这篇博客:简单工厂和工厂方法模式
2.1 优点
1、降低了客户与具体实现的耦合(相较不使用简单工厂而言)。
封装了细节,客户只需调用工厂接口,不必关心如何创建产品,只关心使用产品;
2.2 缺点
1、工厂类对产品的耦合较强
集中了所有产品的创建逻辑,模块与模块之间耦合在一个类里。 工厂崩、系统也崩;
2、违反“开放-关闭原则”
添加新产品,除了添加新产品代码外,还需要修改工厂逻辑,添加分支处理;
3. 怎样使用简单工厂模式?
3.1 方法
以四则运算器工厂为例:
1、简单工厂类提供静态方法,通过
swich...case...
生成对应运算器实例。
返回运算器的基类,将分支的子类指针赋值给了基类,实现客户与具体产品的解耦。
2、提供运算器基类,实现通用方法,提供抽象的结果纯虚接口
getResult()
。
3、加减乘除子类分别实现
getResult()
接口,应用了多态运行时生成对象的特点,通过基类指针调用该接口,完成客户端加减乘除功能的实现。
3.2 UML类图
4. 实例
4.1 结果(结论先行)
4.1.1 main.cpp
#include "Operation.h"
#include "OperationFactory.h"
using namespace std;
void test()
{
double numA = 20, numB = 10;
cout << "A = " << numA << "\tB = " << numB << endl;
Operation* oper = OperationFactory::createOperation('+');
oper->setNumberA(numA);
oper->setNumberB(numB);
cout << "add result = " << oper->getResult() << endl;
oper = OperationFactory::createOperation('-');
oper->setNumberA(numA);
oper->setNumberB(numB);
cout << "sub result = " << oper->getResult() << endl;
oper = OperationFactory::createOperation('*');
oper->setNumberA(numA);
oper->setNumberB(numB);
cout << "mul result = " << oper->getResult() << endl;
oper = OperationFactory::createOperation('/');
oper->setNumberA(numA);
oper->setNumberB(numB);
cout << "div result = " << oper->getResult() << endl;
}
int main()
{
test();
system("pause");
return 0;
}
4.2 具体实现
4.2.1 简单工厂的静态接口
1、OperationFactory.h
#pragma once
#include "Operation.h"
#include "OperationAdd.h"
#include "OperationMul.h"
#include "OperationDiv.h"
#include "OperationSub.h"
class OperationFactory
{
public:
static Operation* createOperation(char sOperate);
};
Operation* OperationFactory::createOperation(char sOperate)
{
Operation* oper = nullptr;
switch (sOperate)
{
case '+':
oper = new OperationAdd();
break;
case '-':
oper = new OperationSub();
break;
case '*':
oper = new OperationMul();
break;
case '/':
oper = new OperationDiv();
break;
default:
break;
}
return oper;
}
4.2.2 四则运算符继承体系代码
1、Operation.h
#pragma once
#include <iostream>
class Operation
{
public:
Operation() {}
virtual ~Operation() {}
virtual double getResult() = 0;
double getNumberA() { return m_numberA; }
double getNumberB() { return m_numberB; }
void setNumberA(const double& num) { m_numberA = num; }
void setNumberB(const double& num) { m_numberB = num; }
protected:
double m_numberA{ 0 };
double m_numberB{ 0 };
};
2、OperationAdd.h
#pragma once
#include "Operation.h"
class OperationAdd :
public Operation
{
public:
OperationAdd() {}
virtual ~OperationAdd() {}
double getResult() override { return m_numberA + m_numberB; }
};
3、OperationSub.h
#pragma once
#include "Operation.h"
class OperationSub :
public Operation
{
public:
OperationSub() {}
virtual ~OperationSub() {}
double getResult() override { return m_numberA - m_numberB; }
};
4、OperationMul.h
#pragma once
#include "Operation.h"
class OperationMul :
public Operation
{
public:
OperationMul() {}
virtual ~OperationMul() {}
double getResult() override { return m_numberA * m_numberB; }
};
5、OperationDiv.h
#pragma once
#include "Operation.h"
class OperationDiv :
public Operation
{
public:
OperationDiv() {}
virtual ~OperationDiv() {}
double getResult() override
{
double result = 0;
if (m_numberB == 0)
throw new std::exception("除数不能为0。");
result = m_numberA / m_numberB;
return result;
}
};
此为《大话设计模式》学习心得系列 P9~~
简单工厂进阶一:《大话设计模式》C++实现:08 工厂模式
简单工厂进阶二:《大话设计模式》C++实现:01 简单工厂模式(优化,使用宏注册工厂)