24行为型模式之解释模式

概念

角色和职责

Context

　　解释器上下文环境类。用来存储解释器的上下文环境，比如需要解释的文法等。

AbstractExpression   

 　　解释器抽象类。

ConcreteExpression

　　解释器具体实现类。

适用于:

 　　解释器根据中介结果实现对应的运算。

案例

//加号、减号解释器，根据上下文储存内容再加载到解释器中，进行对应的运算

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

//保存中间结果
class Context
{
public:
	Context(int num)
	{
		m_num = num;
	}
public:
	void setNum(int num)
	{
		m_num = num;
	}
	int getNum()
	{
		return m_num;
	}
	void setRes(int res)
	{
		m_res = res;
	}
	int getRes()
	{
		return m_res;
	}

private:
	int m_num;
	int m_res;

};
//加号解释器
class Expression
{
public:
	virtual void interpreter(Context *context) = 0;
};

class PlusExpression : public Expression
{
public:
	virtual void interpreter(Context *context)
	{
		int num = context->getNum();
		num ++ ;
		context->setNum(num);
		context->setRes(num);
	}
};
//减法解释器
class MinusExpression : public Expression
{
public:
	virtual void interpreter(Context *context)
	{
		int num = context->getNum();
		num -- ;
		context->setNum(num);
		context->setRes(num);
	}
};

void main()
{
	Context *pcxt = new Context(10);
	Expression *e1 = new PlusExpression;
	e1->interpreter(pcxt);
	cout << "PlusExpression:" << pcxt->getRes() << endl;

	Expression *e2 = new MinusExpression;
	e2->interpreter(pcxt);
	cout << "MinusExpression:" << pcxt->getRes() << endl;

	delete e2;
	delete e1;
	system("pause");
	return ;
}