简单工厂模式

看了<<大话设计模式>>, 照着写了一个简单工厂模式的计算器, 慢慢来, 不急.

#include <iostream>
#include <stdexcept>
using namespace std;


class Operation
{
public:
	virtual float Operating() = 0;
public:
	float numberleft;
	float numberright;
};

class OperationAdd : public	Operation
{
public:
	float Operating()
	{
		return (numberleft + numberright);
	}
};

class OperationSub : public Operation
{
public:
	float Operating()
	{
		return (numberleft - numberright);
	}
};

class OperationMul : public Operation
{
public:
	float Operating()
	{
		return (numberleft * numberright);
	}
};

class OperationDiv : public Operation
{
public:
	float Operating()
	{
		if (numberright == 0)	   //抛出异常
			throw std::out_of_range("参数异常: 除法右值不能为0");
		return (numberleft / numberright);
	}	
};

// 运算符工厂
class OperationFactory
{
public:
	OperationFactory()
	{
		op = NULL;
	}

	void Operating(float numberleft, char operate, float numberright)
	{
	
		switch(operate)
		{
		case ('+'):
			op = new OperationAdd;
			break;
		case ('-'):
			op = new OperationSub;
			break;
		case ('*'):
			op = new OperationMul;
			break;
		case ('/'):
			op = new OperationDiv;
			break;
		default:
			throw std::out_of_range("参数异常: 没有输入正确的运算符");
			break;
		}

		op->numberleft = numberleft;
		op->numberright = numberright;
	}

	float GetResult()
	{
		return op->Operating();
	}
private:
	Operation * op;
};

void Operate()
{
	float numberA;
	float numberB;
	char operate;
	cout << "请输入数字A :";
	cin >> numberA;
	cout << "请输入运算符:";
	cin >> operate;
	cout << "请输入数字B :";
	cin >> numberB;

	OperationFactory *opef = new OperationFactory;
	opef->Operating(numberA, operate, numberB);
	cout << "结果是:" << opef->GetResult() << endl;
}

int main()
{
	//Operate();
	try
	{
		Operate();
	}
	catch (exception &e) // 异常要用引用收
	{
		cout << e.what() << endl;
	}
	catch (...)
	{

	}
	
	system("pause");
	return 0;
}