学习笔记：visitor模式和双分派

来源：互联网发布：windows xp iis配置编辑：程序博客网时间：2024/05/16 04:09
#include "stdafx.h"#include <iostream>using namespace std;class CEmployee;class CProgrammer;class CManager;class CCEO;class IVisitor{public:    virtual void Visit(CEmployee* p) = 0;    virtual void Visit(CProgrammer* p) = 0;    virtual void Visit(CManager* p) = 0;    virtual void Visit(CCEO* p) = 0;};class CEmployee {public:    virtual void Accept(IVisitor *v)=0;    virtual int getSalary(){        return 0;    }};class CProgrammer : public CEmployee{public:    virtual void Accept(IVisitor *v){        v->Visit(this);    }    virtual int getSalary(){        return 100;    } };class CJuniorProgrammer : public CEmployee{public:    virtual void Accept(IVisitor *v){        v->Visit(this);    }    virtual int getSalary(){        return 500;    } };class CVeteranProgrammer : public CEmployee{public:    virtual void Accept(IVisitor *v){        v->Visit(this);    }    virtual int getSalary(){        return 1000;    } };class CManager : public CEmployee{public:    virtual void Accept(IVisitor *v){        v->Visit(this);    }    virtual int getSalary(){        return 1000;    }    int getBonus(){        return 1000;    }};class CCEO : public CEmployee{public:    virtual void Accept(IVisitor *v){        v->Visit(this);    }    int yearly_salary(){        return 120000;    }};class SalaryVisitor:public IVisitor{public:    SalaryVisitor():sum_(0){}    virtual void Visit(CEmployee* p){        sum_ += p->getSalary();    }    virtual void Visit(CProgrammer* p){        sum_ += p->getSalary();    }    virtual void Visit(CManager* p){        sum_ += p->getSalary();        sum_ += p->getBonus();    }    virtual void Visit(CCEO* p){        sum_ += (p->yearly_salary() / 12);    }public:    int GetTotalSalary(){        return sum_;    }private:    int sum_;};//优点：CEmployee继承体系基本不会被冲击。如果SalaryVisitor算法有问题，只是更改SalaryVisitor即可。需要预先在CEmployee继承体系嵌入virtual void Accept(IVisitor *v)=0;，如果不让动旧代码，此模式失败。如果增加新的雇员类型，就需要动IVisitor。同理，必将引起底层代码重编译。int main() {    IVisitor* pv = new SalaryVisitor();    CEmployee* pe = new CCEO();    pe->Accept(pv);        return 0;}
0 0