設計模式入門1——簡單工廠模式（OperationFactory）

        從設計模式的類型上來說，簡單工廠模式是屬於創建型模式，又叫做靜態工廠方法（Static Factory Method）模式，但不屬於23種GOF設計模式之一。簡單工廠模式是由一個工廠對象決定創建出哪一種產品類的實例。簡單工廠模式是工廠模式家族中最簡單實用的模式，可以理解爲是不同工廠模式的一個特殊實現。[From baike.baidu.com]

/*******************************************************/
//名稱：簡單工廠模式（OperationFactory）
//時間：2014年4月4日11:49:21
//作者：Lynch
/*******************************************************/

#pragma once
#include"OperationFactory.h"

int main()
{
	int a,b;
	char oper;
	while(true)
	{
		cout<<"Please input num1,num2,and operators(+,-,*,/,^)"<<endl;
		cin>>a>>b>>oper;
		OperationFactory *of=new OperationFactory();	//創建操作符工廠模式
		Operation *op=of->CreateOperation(oper);		//根據操作符創建對應的類
		op->setNum1(a);
		op->setNum2(b);
		cout<<op->getResult()<<endl;
		delete op;
		delete of;
	}
	
	return 0;
}

#pragma once
#include"Operation.h"		//基類
#include"AddOperation.h"	//加法類
#include"SubOperation.h"	//減法類
#include"MulOperation.h"	//乘法類
#include"DivOperation.h"	//除法類
#include"InvOperation.h"	//乘方類
class OperationFactory
{
public:
	Operation *CreateOperation(char oper)
	{
		Operation *op=NULL;
		switch(oper)
		{
		case'+':
			op=new AddOperation();
			break;
		case'-':
			op=new SubOperation();
			break;
		case'*':
			op=new MulOperation();
			break;
		case'/':
			op=new DivOperation();
			break;
		case'^':
			op=new InvOperation();
			break;
		default:
			break;
		}
		return op;
	}
};

#pragma once
#include<iostream>
using namespace std;

class Operation
{
public:
	void setNum1(int num1)
	{
		this->num1=num1;
	}

	void setNum2(int num2)
	{
		this->num2=num2;
	}

	virtual int getResult()=0;	//純虛函數，不允許Operation類實例化對象

protected:
	int num1;
	int num2;
};

#pragma once
#include"Operation.h"

class AddOperation:public Operation
{
public:

	virtual int getResult()
	{
		return num1+num2;
	}

};

#pragma once
#include"Operation.h"

class DivOperation:public Operation
{
public:

	virtual int getResult()
	{
		if(num2==0)
		{
			cerr<<"Cannot be divided by 0!"<<endl;
			exit(1);
		}
		return num1/num2;
	}

};

#pragma once
#include"Operation.h"
#include<cmath>
//involution乘方運算
class InvOperation:public Operation
{
public:

	virtual int getResult()
	{
		return pow((double)num1,(double)num2);
	}

};

#pragma once
#include"Operation.h"

class MulOperation:public Operation
{
public:

	virtual int getResult()
	{
		return num1*num2;
	}

};

#pragma once
#include"Operation.h"

class SubOperation:public Operation
{
public:

	virtual int getResult()
	{
		return num1-num2;
	}

};

代碼佈局：

運行效果：