设计模式复习-迭代器模式

Iterator.H
#pragma once
#include <list>
#include <windows.h>
using namespace std;

/*
设计模式-迭代器模式（Iterator）
提供一种方法顺序访问一个聚合对象中的各个元素，而不暴露该对象内部表示。
(现在好多语言都已经内置实现了这个功能了，所以实际用途不大，
但是建议写一下，实现过程价值远远大于使用价值。)
*/

class Iterator{//迭代器抽象类

public:
	virtual void * First() = 0;
	virtual void * Next() = 0;
	virtual BOOL IsDone() = 0;
	virtual void * CurrentItem() = 0;
};

class CAggregate {//聚集抽象类

public:
	virtual Iterator * CreateIterator() = 0;
	virtual void Insert(void * const pNode) = 0;
	virtual void Remove(void * const pNode) = 0;
};

class CConcreteAggregate :public CAggregate {//具体聚集类

public:
	list<void*>mpItems;
	CConcreteAggregate();
	void Clear();
	Iterator * CreateIterator();
	void Insert(void * const pNode);
	void Remove(void * const pNode);
};

class CConcreteIterator : public Iterator {//具体的迭代器类

private:
	CConcreteAggregate *mpAggregate = NULL;
	int mnCurrent = 0;
public:
	CConcreteIterator(CConcreteAggregate * pAggregate);
	 void * First();
	 void * Next();
	 BOOL IsDone();
	 void * CurrentItem();
};



Iterator.CPP
#include "stdafx.h"
#include "Iterator.h"


CConcreteAggregate::CConcreteAggregate() {
	mpItems.clear();
}

void CConcreteAggregate::Clear() {
	for each(auto i in mpItems) {
		delete i;
	}
}

Iterator * CConcreteAggregate::CreateIterator() {
	return new CConcreteIterator(this);
}

void CConcreteAggregate::Insert(void * const pNode) {
	mpItems.push_back(pNode);
}
void CConcreteAggregate::Remove(void * const pNode) {
	mpItems.remove(pNode);
}

CConcreteIterator::CConcreteIterator(CConcreteAggregate * pAggregate) {
	mpAggregate = pAggregate;
	mnCurrent = 0;
}

void * CConcreteIterator::First() {
	return mpAggregate->mpItems.size() == 0 ? NULL :
		*(mpAggregate->mpItems.begin());
}
void * CConcreteIterator::Next() {
	if (IsDone()) return NULL;
	int nSubscript = 0;
	mnCurrent++;
	for each(auto i in mpAggregate->mpItems) {
		if (nSubscript++ == mnCurrent + 1) {
			return i;
		}
	}
}
BOOL CConcreteIterator::IsDone() {
	return mnCurrent >= mpAggregate->mpItems.size();
}
void * CConcreteIterator::CurrentItem() {
	int nSubscript = 0;
	for each(auto i in mpAggregate->mpItems) {
		if (nSubscript++ == mnCurrent) {
			return i;
		}
	}
	return NULL;
}

#pragma once
#include "stdafx.h"
#include "Iterator.h"
#include<string>
#include<iostream>
using namespace std;

int main() {

	CConcreteAggregate *pA = new CConcreteAggregate();
	pA->Insert(new string("node-1"));
	pA->Insert(new string("node-2"));
	string * pStr = new string("node-3");
	pA->Insert(pStr);

	Iterator *pIteratorA = new CConcreteIterator(pA);
	while (!pIteratorA->IsDone()) {
		cout << *((string*)pIteratorA->CurrentItem()) << endl;
		pIteratorA->Next();
	}

	pA->Remove(pStr);
	Iterator *pIteratorB = pA->CreateIterator();
	while (!pIteratorB->IsDone()) {
		cout << *((string*)pIteratorB->CurrentItem()) << endl;
		pIteratorB->Next();
	}

	pA->Clear();
	delete pIteratorA;
	delete pIteratorB;
	delete pA;
	delete pStr;

	getchar();
	return 0;
}