设计模式之五-Facade模式

Facade门面模式，也是比较常用的一种模式，其含义是为子系统中的一组接口提供一个一致的界面， Facade 模式定义了一个高层接口，这个接口使得这一子系统更加容易使用。简单说，就是将复杂的逻辑封装起来，对外公开简单的接口，由客户程序调用。 
以收发信件和警察检查实例为例 
说明：邮局对外只有一个窗口，接收信件内容和邮件地址。对内调用邮件处理的4个函数。将复杂逻辑封装在邮局的里面，当需要增加警察来检查信件时，只需在邮局内增加警察检查信件的方法。 
注意：将复杂逻辑封装起来，对外只有一个简单的接口。

抽象信件处理类

//ILetterProcess.h
#pragma once
#include <iostream>
using std::string;
class ILetterProcess
{
public:
    ILetterProcess(void);
    virtual ~ILetterProcess(void);
    virtual void WriteContext(string context) = 0;
    virtual void FillEnvelope(string address) = 0;
    virtual void LetterIntoEnvelope() = 0;
    virtual void SendLetter() = 0;
};

//ILetterProcess.cpp

#include "StdAfx.h"
#include "ILetterProcess.h"
ILetterProcess::ILetterProcess(void)
{
}
ILetterProcess::~ILetterProcess(void)
{
}

信件处理实现类

//LetterprocessImpl.h

#pragma once
#include "iletterprocess.h"
class CLetterProcessImpl :
    public ILetterProcess
{
public:
    CLetterProcessImpl(void);
    ~CLetterProcessImpl(void);

    void WriteContext(string context);
    void FillEnvelope(string address);
    void LetterIntoEnvelope();
    void SendLetter();
};

//LetterProcessImpl.cpp

#include "StdAfx.h"
#include "LetterProcessImpl.h"
#include <iostream>
using std::string;
using std::cout;
using std::endl;
CLetterProcessImpl::CLetterProcessImpl(void)
{
}
CLetterProcessImpl::~CLetterProcessImpl(void)
{
}
void CLetterProcessImpl::WriteContext(string context)
{
    cout << "填写信的内容... ..." << endl;
}
void CLetterProcessImpl::FillEnvelope(string address)
{
    cout << "填写收件人地址及姓名... ..." << endl;
}
void CLetterProcessImpl::LetterIntoEnvelope()
{
    cout << "把信放到信封中..." << endl;
}
void CLetterProcessImpl::SendLetter()
{
    cout << "邮递信件..." << endl;
}

邮局处理信件类

//ModenPostOffice.h

#pragma once
#include "ILetterProcess.h"
#include "LetterProcessImpl.h"
#include "LetterPolice.h"
#include <iostream>
using std::string;
class CModenPostOffice
{
public:
    CModenPostOffice(void);
    ~CModenPostOffice(void);
    void SendLetter(string context, string address);
private:
    ILetterProcess *m_pLetterProcess;
    CLetterPolice *m_pLetterPolice;
};

//ModenPostOffice.cpp

#include "StdAfx.h"
#include "ModenPostOffice.h"
CModenPostOffice::CModenPostOffice(void)
{
    this->m_pLetterProcess = new CLetterProcessImpl();
    this->m_pLetterPolice = new CLetterPolice();
}
CModenPostOffice::~CModenPostOffice(void)
{
    delete m_pLetterProcess;
    delete m_pLetterPolice;
}
void CModenPostOffice::SendLetter( string context, string address )
{
    //帮忙写信
    m_pLetterProcess->WriteContext(context);
    //写好信封
    m_pLetterProcess->FillEnvelope(address);
    //警察要检查信件了
    m_pLetterPolice->CheckLetter(m_pLetterProcess);
    //把信放到信封中
    m_pLetterProcess->LetterIntoEnvelope();
    //邮递信件
    m_pLetterProcess->SendLetter();
}

测试

//Facade.cpp

#include "stdafx.h"
#include "ILetterProcess.h"
#include "LetterProcessImpl.h"
#include "ModenPostOffice.h"
#include<iostream>
using std::string;
using std::cout;
using std::endl;
void DoItByPostOffice()
{
    CModenPostOffice modenPostOffice;
    string context = "Hello, It‘s me, do you know who I am? I‘m your old lover. I‘d like to ... ...";
    string address = "Happy Road No. 666, Beijing City, China";
    modenPostOffice.SendLetter(context, address);
}
void DoItYourself()
{
    ILetterProcess *pLetterProcess = new CLetterProcessImpl();
    pLetterProcess->WriteContext("Hello, It‘s me, do you know who I am? I‘m your old lover. I‘d like to ... ...");
    pLetterProcess->FillEnvelope("Happy Road No. 666, Beijing City, China");
    pLetterProcess->LetterIntoEnvelope();
    pLetterProcess->SendLetter();
    delete pLetterProcess;
}
int _tmain(int argc, _TCHAR* argv[])
{
    //现在的调用方式。对于客户来说确实简单多了。
    //如需要增加逻辑，例如让警察来检查邮件。可以在邮局里完成这项工作。
    DoItByPostOffice();

    //原来的调用方式。
    DoItYourself();

    system(“pause”);

    return 0;
}

转载自http://blog.csdn.net/phiall/article/details/52199659