设计模式C++学习笔记之十四（Iterator迭代器模式）

设计模式C++学习笔记之十四（Iterator迭代器模式）

14.1.解释

概念：提供一种方法顺序访问一个聚合对象中各个元素，而又不需暴露该对象的内部表示。

main()，客户

IProject，产品接口

CProject，产品类

IIterator，迭代器接口

IProjectIterator，产品迭代器接口

CProjectIterator，产品迭代器实现类

说明：CProject实现产品类，能够返回一个迭代器的指针。这个迭代器将封装产品类里的一个数组。所以迭代器在运行Next函数时，可以遍历这个数组的所有元素。

简单来说，就是用代码实现vector<int>::iterator或vector<int>::const_iterator。

我们来看代码：

//IProject.h

#pragma once

#include "IProjectIterator.h"

#include <iostream>

using std::string;

class IProject

{

public:

    IProject(void)

    {

    }

    virtual ~IProject(void)

    {

    }

    virtual void Add(string name, int num, int cost) = 0;

    virtual string GetProjectInfo() = 0;

    virtual IProjectIterator* GetIterator() = 0;

    virtual void Erase() = 0;

};

//Project.h

#pragma once

#include "iproject.h"

#include "IProjectIterator.h"

#include <iostream>

#include <vector>

using std::string;

using std::vector;

class CProject :

    public IProject

{

public:

    CProject(void);

    CProject(string name, int num, int cost);

    ~CProject(void);

    string GetProjectInfo();

    void Add(string name, int num, int cost);

    IProjectIterator * GetIterator();

    void Erase();

private:

    string m_name;

    int m_num;

    int m_cost;

    vector<IProject*> m_projectList;

};

//Project.cpp

#include "StdAfx.h"

#include "Project.h"

#include "..\CommonDeclare\Convert.h"

#include "ProjectIterator.h"

#include <iostream>

#include <vector>

using std::string;

using std::vector;

CProject::CProject( void )

{

    m_name = "";

    m_num = 0;

    m_cost = 0;

}

CProject::CProject(string name, int num, int cost) :m_name(name), m_num(num), m_cost(cost)

{

}

CProject::~CProject(void)

{

}

string CProject::GetProjectInfo()

{

    string info = "";

    info.append("项目名称是：");

    info.append(this->m_name);

    info.append("\t项目人数：");

    info.append(CConvert::ToString(m_num));

    info.append("\t项目费用：");

    info.append(CConvert::ToString(m_cost));

    return info;

}

void CProject::Add( string name, int num, int cost )

{

    this->m_projectList.push_back(new CProject(name, num, cost));

}

IProjectIterator * CProject::GetIterator()

{

    return new CProjectIterator(this->m_projectList);

}

void CProject::Erase()

{

    vector<IProject*>::reverse_iterator projectDelIt = m_projectList.rbegin();

    for (; projectDelIt != m_projectList.rend(); projectDelIt++)

    {

        delete (*projectDelIt);

        (*projectDelIt) = NULL;

    }

    m_projectList.clear();

}

//IIterator.h

#pragma once

class IProject;

class IIterator

{

public:

    IIterator(void)

    {

    }

    virtual ~IIterator(void)

    {

    }

    virtual bool HasNext() = 0;

    virtual IProject * Next() = 0;

};

//IProjectIterator.h

#pragma once

#include "iiterator.h"

class IProject;

class IProjectIterator :

    public IIterator

{

public:

    IProjectIterator(void)

    {

    }

    virtual ~IProjectIterator(void)

    {

    }

    virtual bool HasNext() = 0;

    virtual IProject * Next() = 0;

};

//ProjectIterator.h

#pragma once

#include "iprojectiterator.h"

#include "IProject.h"

#include <vector>

using std::vector;

class CProjectIterator :

    public IProjectIterator

{

public:

    CProjectIterator(vector<IProject *> pl);

    ~CProjectIterator(void);

    bool HasNext();

    IProject * Next();

private:

    vector<IProject *> m_projectList;

    size_t m_currentItem;

};

//ProjectIterator.cpp

#include "StdAfx.h"

#include "ProjectIterator.h"

CProjectIterator::CProjectIterator(vector<IProject *> pl) : m_projectList(pl)

{

    m_currentItem = 0;

}

CProjectIterator::~CProjectIterator(void)

{

}

bool CProjectIterator::HasNext()

{

    bool b = true;

    if (m_currentItem >= m_projectList.size())

        b = false;

    return b;

}

IProject * CProjectIterator::Next()

{

    IProject *pp = m_projectList.at(m_currentItem ++);

    return pp;

}

// Iterator.cpp

#include "stdafx.h"

#include "IProject.h"

#include "Project.h"

#include "..\CommonDeclare\Convert.h"

#include "ProjectIterator.h"

#include <iostream>

#include <vector>

using std::vector;

using std::cout;

using std::endl;

void DoIt()

{

    cout << "----------未使用迭代模式----------" << endl;

    vector<IProject*> projectList;

    projectList.push_back(new CProject("星球大战项目", 10, 100000));

    projectList.push_back(new CProject("扭转时空项目", 100, 10000000));

    projectList.push_back(new CProject("超人改造项目", 10000, 1000000000));

    for (int i = 4; i < 6; i ++)

    {

        string name = "";

        name.append("第");

        name.append(CConvert::ToString(i));

        name.append("个项目");

        projectList.push_back(new CProject(name, i * 5, i * 1000000));

    }

    vector<IProject*>::const_iterator projectIt = projectList.begin();

    for (; projectIt != projectList.end(); projectIt++)

        cout << (*projectIt)->GetProjectInfo().c_str() << endl;

    vector<IProject*>::reverse_iterator projectDelIt = projectList.rbegin();

    for (; projectDelIt != projectList.rend(); projectDelIt++)

    {

        delete (*projectDelIt);

        (*projectDelIt) = NULL;

    }

    projectList.clear();

}

void DoNew()

{

    cout << "----------使用迭代模式----------" << endl;

    IProject *pproject = new CProject();

    pproject->Add("星球大战项目", 10, 100000);

    pproject->Add("扭转时空项目", 100, 10000000);

    pproject->Add("超人改造项目", 10000, 1000000000);

    for (int i = 4; i < 6; i ++)

    {

        string name = "";

        name.append("第");

        name.append(CConvert::ToString(i));

        name.append("个项目");

        pproject->Add(name, i * 5, i * 1000000);

    }

    IProjectIterator *pprojectIt = pproject->GetIterator();

    while(pprojectIt->HasNext())

    {

        IProject *p = dynamic_cast<IProject*>(pprojectIt->Next());

        cout << p->GetProjectInfo().c_str() << endl;

    }

    delete pprojectIt;

    pprojectIt = NULL;

    pproject->Erase();

    delete pproject;

    pproject = NULL;

}

int _tmain(int argc, _TCHAR* argv[])

{

    //
a138
使用Iterator模式之前

    DoIt();

    //使用Iterator

    DoNew();

    _CrtSetDbgFlag(_CRTDBG_LEAK_CHECK_DF | _CRTDBG_ALLOC_MEM_DF);

    _CrtDumpMemoryLeaks();

    return 0;

}



这个模式，可能有一点绕，需要再仔细的思考一番。本来希望把模式的工作方式，用最简单易懂的语言来总结，但其实这个总结更难。简单的模式还容易些理解，也容易总结，复杂的就难了。打算在之后，学习数据结构的过程中，都总结出这样一句话来。很期待后面对数据结构的学习，发现自己越来越爱学习了。