[设计模式]开闭原则

Posted 2021-06-27 Wecccccccc

开闭原则:

对扩展开放，对修改关闭。

增加功能是提过增加代码来实现的，而不是去修改源代码。

代码如下:

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

class Caculaor
{
public:
	Caculaor(int a,int b,string  c):a(a),b(b),myOperator(c){}

	int getResult()
	{
		if (myOperator.compare("+") == 0)
		{
			return a + b;
		}
		else if (myOperator.compare("-") == 0)
		{
			return a - b;
		}
		else if (myOperator.compare("*")==0)
		{
			return a * b;
		}
		else if (myOperator.compare("/") == 0)
		{
			return a / b;
		}
	}

private:
	int a;
	int b;
	string myOperator;
};


void test01()
{
	Caculaor *a = new Caculaor(10, 10, "+");
	cout<<a->getResult()<<endl;
}

int main()
{
	test01();
	return 0;
}

测试结果:

缺点:
如果增加取模的运算，需要修改getResult成员方法，如果增加新功能的情况下要修改源代码，那么就会有出错的可能性，我们应该在增加新的功能时候，不能影响其他已经完成的功能，这就是对修改关闭，对扩展开放，叫做开闭原则。

开闭原则
代码如下:

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

class AbstractCaculator {
public:
	virtual int getResult() = 0;
	virtual void setNumber(int a, int b) = 0;
};


class PlusCaculator :public AbstractCaculator
{
public:

	virtual void setNumber(int a, int b)
	{
		this->a = a;
		this->b = b;
	}

	virtual int getResult()
	{
		return a + b;
	}

private:
	int a;
	int b;
};


class MinuteCaculator :public AbstractCaculator
{
public:

	virtual void setNumber(int a, int b)
	{
		this->a = a;
		this->b = b;
	}

	virtual int getResult()
	{
		return a - b;
	}

private:
	int a;
	int b;
};


class MultiplyCaculator :public AbstractCaculator
{
public:

	virtual void setNumber(int a, int b)
	{
		this->a = a;
		this->b = b;
	}

	virtual int getResult()
	{
		return a * b;
	}

private:
	int a;
	int b;
};

class DivideCaculator :public AbstractCaculator
{
public:

	virtual void setNumber(int a, int b)
	{
		this->a = a;
		this->b = b;
	}

	virtual int getResult()
	{
		return a / b;
	}

private:
	int a;
	int b;
};

//取模计算器  通过增加代码来实现
class MoldTakingCaculator :public AbstractCaculator
{
public:

	virtual void setNumber(int a, int b)
	{
		this->a = a;
		this->b = b;
	}

	virtual int getResult()
	{
		return a % b;
	}

private:
	int a;
	int b;
};



void test01()
{
	AbstractCaculator *a = new PlusCaculator;
	a->setNumber(10, 10);
	cout << a->getResult() << endl;
}

int main()
{
	test01();
	return 0;
}

测试结果: