1.解釋器模式簡介

? ?解釋器模式（Interpreter Pattern）提供了評估語言的語法或表達式的方式，它屬于行為型模式。這種模式實現(xiàn)了一個表達式接口，該接口解釋一個特定的上下文。這種模式被用在 SQL 解析、符號處理引擎等。

2.源碼實現(xiàn)

#include <iostream>
#include <string>

using namespace std;

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;
};

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);
    }
};

class MinusExpression : public Expression
{
public:
    virtual void interpreter(Context *context)
    {
        int num = context->getNum();
        num--;
        context->setNum(num);
        context->setRes(num);
    }
};

int main(int argc, char **argv)
{
    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 e1;
    delete e2;

    delete pcxt;

    return 0;
}

3.編譯源碼

$ g++ -o example example.cpp

4.運行及其結(jié)果

$ ./example
PlusExpression: 11
MinusExpression: 10