[設計模式]Iterator迭代器模式

問題

iterator模式應該是最為熟悉的模式了，最簡單的證明就是在實現Composite模式，Flyweight模式，Observer模式中就直接用到了STL提供的Iterator來遍曆Vector或者List資料結構。

Iterator模式也正是用來解決對一個彙總對象的遍曆問題，將對彙總的遍曆封裝到一個類中進行，這樣就避免了暴露這個彙總對象的內部表示的可能。

iterator迭代器模式

提供一種方法順序訪問一個彙總對象中各個元素, 而又不需暴露該對象的內部表示。

小demo

iterator.h

#ifndef ITERATOR_H#define ITERATOR_Htypedef int DATA;class Iterater;// 容器的抽象基類class Aggregate{public:virtual ~Aggregate(){}virtual Iterater* CreateIterater(Aggregate *pAggregate) = 0;virtual int GetSize() = 0;virtual DATA GetItem(int nIndex) = 0;};// 迭代器的抽象基類class Iterater{public:virtual ~Iterater(){}virtual void First()= 0;virtual void Next()= 0;virtual bool IsDone()= 0;virtual DATA CurrentItem()= 0; };// 一個具體的容器類,這裡是用數組表示class ConcreateAggregate: public Aggregate{public:ConcreateAggregate(int nSize);virtual ~ConcreateAggregate();virtual Iterater* CreateIterater(Aggregate *pAggregate);virtual int GetSize();virtual DATA GetItem(int nIndex);private:int m_nSize;DATA *m_pData;};// 訪問ConcreateAggregate容器類的迭代器類class ConcreateIterater : public Iterater{public:ConcreateIterater(Aggregate* pAggregate);virtual ~ConcreateIterater(){}virtual void First();virtual void Next();virtual bool IsDone();virtual DATA CurrentItem();private:Aggregate  *m_pConcreateAggregate;intm_nIndex;};#endif

 

iterator.cpp

#include <iostream>#include "Iterator.h"ConcreateAggregate::ConcreateAggregate(int nSize) : m_nSize(nSize), m_pData(NULL){m_pData = new DATA[m_nSize];for (int i = 0; i < nSize; ++i){m_pData[i] = i;}}ConcreateAggregate::~ConcreateAggregate(){delete [] m_pData;m_pData = NULL;}Iterater* ConcreateAggregate::CreateIterater(Aggregate *pAggregate){return new ConcreateIterater(this);}int ConcreateAggregate::GetSize(){return m_nSize;}

 

main.cpp

#include "Iterator.h"#include <iostream>int main(){Aggregate* pAggregate = new ConcreateAggregate(4);Iterater*  pIterater  = new ConcreateIterater(pAggregate);for (; false == pIterater->IsDone(); pIterater->Next()){std::cout << pIterater->CurrentItem() << std::endl;}    system("pause");return 0;}