设计模式C++学习笔记之十三（Decorator装饰模式）

 

装饰模式，动态地给一个对象添加一些额外的职责。就增加功能来说，Decorator模式相比生成子类更为灵活。

13.1.解释

main()，老爸

ISchoolReport，成绩单接口

CFourthGradeSchoolReport，四年级成绩单

ReportDecorator，成绩单装饰器基类

HighScoreDecorator，最高分装饰器

SortDecorator，班级排名装饰器

说明：对“四年级成绩单”进行装饰，ReportDecorator必然有一个private变量指向ISchoolReport。

注意：

看代码：

// Decorator.cpp//主程序
#include "stdafx.h"
#include "ISchoolReport.h"
#include "FouthGradeSchoolReport.h"
#include "SugarFouthGradeSchoolReport.h"
#include "HighScoreDecorator.h"
#include "SortDecorator.h"
#include <iostream>
using std::cout;
using std::endl;
void DoIt()
{
    ISchoolReport *psr = new CSugarFouthGradeSchoolReport();
    psr->Report();//看成绩单
    psr->Sign("老三");//很开心，就签字了
    delete psr;
}
void DoNew()
{
    cout << "----------分部分进行装饰----------" << endl;
    ISchoolReport *psr = new CFouthGradeSchoolReport();//原装成绩单
    //
    ISchoolReport *pssr = new CSortDecorator(psr);//又加了成绩排名的说明
    ISchoolReport *phsr = new CHighScoreDecorator(pssr);//加了最高分说明的成绩单
    phsr->Report();//看成绩单
    phsr->Sign("老三");//很开心，就签字了
    
    //先装饰哪个不重要，顺序已经在装饰内部确定好，但一定要调用最后一个装饰器的接口。
    //ISchoolReport *phsr = new CHighScoreDecorator(psr);//加了最高分说明的成绩单
    //ISchoolReport *pssr = new CSortDecorator(phsr);//又加了成绩排名的说明
    //pssr->Report();//看成绩单
    //pssr->Sign("老三");//很开心，就签字了

delete pssr;
    delete phsr;
    delete psr;
}
int _tmain(int argc, _TCHAR* argv[])
{
    //在装饰之前，可以用继承的办法，来进行简单的修饰
    DoIt();

//但如果需要修饰的项目太多呢？或者装饰的项目不是固定的，继承显然会变得更复杂
    DoNew();

_CrtSetDbgFlag(_CRTDBG_LEAK_CHECK_DF | _CRTDBG_ALLOC_MEM_DF);
    _CrtDumpMemoryLeaks();
    return 0;
}

//ISchoolReport.h

#pragma once
#include <iostream>
using std::string;
class ISchoolReport
{
public:
    ISchoolReport(void)
    {
    }
    virtual ~ISchoolReport(void)
    {
    }
    virtual void Report() = 0;
    virtual void Sign(string name) = 0;
};

//FouthGradeSchoolReport.h

#pragma once
#include "ischoolreport.h"
class CFouthGradeSchoolReport :
    public ISchoolReport
{
public:
    CFouthGradeSchoolReport(void);
    ~CFouthGradeSchoolReport(void);
    void Report();
    void Sign(string name);
};

//FouthGradeSchoolReport.cpp

#include "StdAfx.h"
#include "FouthGradeSchoolReport.h"
#include <iostream>
using std::cout;
using std::endl;
using std::string;
CFouthGradeSchoolReport::CFouthGradeSchoolReport(void)
{
}
CFouthGradeSchoolReport::~CFouthGradeSchoolReport(void)
{
}
void CFouthGradeSchoolReport::Report()
{
    cout << "尊敬的XXX家长：" << endl;
    cout << "......" << endl;
    cout << "语文62  数学65  体育98  自然63" << endl;
    cout << "......" << endl;
    cout << "                家长签名：" << endl;
}
void CFouthGradeSchoolReport::Sign(string name)
{
    cout << "家长签名为：" << name.c_str() << endl;
}

//ReportDecorator.h

#pragma once
#include "ischoolreport.h"
class CReportDecorator :
    public ISchoolReport
{
public:
    CReportDecorator(ISchoolReport *psr);
    virtual ~CReportDecorator(void);
    void Report();
    void Sign(string name);
private:
    ISchoolReport *m_pSchoolReport;
};

//ReportDecorator.cpp

#include "StdAfx.h"
#include "ReportDecorator.h"
#include <iostream>
using std::string;
CReportDecorator::CReportDecorator(ISchoolReport *psr)
{
    this->m_pSchoolReport = psr;
}
CReportDecorator::~CReportDecorator(void)
{
}
void CReportDecorator::Report()
{
    this->m_pSchoolReport->Report();
}
void CReportDecorator::Sign( string name )
{
    this->m_pSchoolReport->Sign(name);
}

//HighScoreDecorator.h

#pragma once
#include "reportdecorator.h"
#include "ISchoolReport.h"
class CHighScoreDecorator :
    public CReportDecorator
{
public:
    CHighScoreDecorator(ISchoolReport *psr);
    ~CHighScoreDecorator(void);
    void Report();
private:
    void ReportHighScore();
};

//HighScoreDecorator.cpp

#include "StdAfx.h"
#include "HighScoreDecorator.h"
#include <iostream>
using std::cout;
using std::endl;
CHighScoreDecorator::CHighScoreDecorator( ISchoolReport *psr ) : CReportDecorator(psr)
{
}
CHighScoreDecorator::~CHighScoreDecorator(void)
{
}
void CHighScoreDecorator::Report()
{
    this->ReportHighScore();
    this->CReportDecorator::Report();
}
void CHighScoreDecorator::ReportHighScore()
{
    cout << "这次考试语文最高是75， 数学是78， 自然是80" << endl;
}

//SortDecorator.h

#pragma once
#include "reportdecorator.h"
#include "ISchoolReport.h"
class CSortDecorator :
    public CReportDecorator
{
public:
    CSortDecorator(ISchoolReport *psr);
    ~CSortDecorator(void);
    void Report();
private:
    void ReportSort();
};
//SortDecorator.cpp

#include "StdAfx.h"
#include "SortDecorator.h"
#include <iostream>
using std::cout;
using std::endl;
CSortDecorator::CSortDecorator( ISchoolReport *psr ) : CReportDecorator(psr)
{
}
CSortDecorator::~CSortDecorator(void)
{
}
void CSortDecorator::ReportSort()
{
    cout << "我是排名第38名..." << endl;
}
void CSortDecorator::Report()
{
    this->CReportDecorator::Report();
    this->ReportSort();
}

这也是一个比较简单的模式，属于行为型模式。