c++设计模式----迭代器模式iterator

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迭代器：
意图：
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。
适用性：
访问一个聚合对象的内容而无需暴露它的内部表示。

支持对聚合对象的多种遍历。

为遍历不同的聚合结构提供一个统一的接口(即, 支持多态迭代)。

#include <iostream>#include <string>#include <vector>using namespace std;class Iterator{public:Iterator(){}virtual ~Iterator(){};virtual string First() = 0;virtual string Next() = 0;virtual string GetCur() = 0;virtual bool IsEnd() = 0;};class Aggregate{public:virtual int Count() = 0;virtual void Push(const string &strValue) = 0;virtual string POp(const int cnt) = 0;virtual Iterator* CreateIterator() = 0;};class ConcreteIterator : public Iterator{public:ConcreteIterator(Aggregate *p_aggregate):m_aggregate(p_aggregate),m_cnt(0){}string First(){return m_aggregate->POp(0);}string Next(){string str;m_cnt++;if (m_cnt < m_aggregate->Count()){str = m_aggregate->POp(m_cnt);}return str;}string GetCur(){return m_aggregate->POp(m_cnt);}bool IsEnd(){return m_cnt >= m_aggregate->Count() ? true : false;}~ConcreteIterator(){ }private:Aggregate *m_aggregate;int m_cnt;};class ConcreteAggregate : public Aggregate{public:ConcreteAggregate() :m_pIterator(NULL){m_vecItem.clear();}~ConcreteAggregate(){if (NULL != m_pIterator){delete m_pIterator;m_pIterator = NULL;}}int Count(){return m_vecItem.size();}void Push(const string &strValue){m_vecItem.push_back(strValue);}string POp(const int cnt){string str;if (cnt < Count()){str = m_vecItem[cnt];}return str;}Iterator* CreateIterator(){if (NULL == m_pIterator){m_pIterator = new ConcreteIterator(this);}return m_pIterator;}private:vector<string> m_vecItem;Iterator *m_pIterator;};int main(){ConcreteAggregate* pName = NULL;pName = new ConcreteAggregate();if (NULL != pName){pName->Push("hello");pName->Push("word");pName->Push("cxue");}Iterator* iter = NULL;iter = pName->CreateIterator();if (NULL != iter){string strItem = iter->First();while (!iter->IsEnd()){cout << iter->GetCur() << " is ok" << endl;iter->Next();}}system("pause");return 0;}

改进一下也许更好懂一点：

#include <iostream>#include <string>#include <vector>using namespace std;class Iterator{public:Iterator(){}virtual ~Iterator(){};virtual string First() = 0;virtual string Next() = 0;virtual string GetCur() = 0;virtual bool IsEnd() = 0;};class Aggregate{public:virtual int Count() = 0;virtual void Push(const string &strValue) = 0;virtual string POp(const int cnt) = 0;};class ConcreteIterator : public Iterator{public:ConcreteIterator(Aggregate *p_aggregate):m_aggregate(p_aggregate),m_cnt(0){}string First(){return m_aggregate->POp(0);}string Next(){string str;m_cnt++;if (m_cnt < m_aggregate->Count()){str = m_aggregate->POp(m_cnt);}return str;}string GetCur(){return m_aggregate->POp(m_cnt);}bool IsEnd(){return m_cnt >= m_aggregate->Count() ? true : false;}~ConcreteIterator(){ }private:Aggregate *m_aggregate;int m_cnt;};class ConcreteAggregate : public Aggregate{public:ConcreteAggregate(){m_vecItem.clear();}~ConcreteAggregate(){}int Count(){return m_vecItem.size();}void Push(const string &strValue){m_vecItem.push_back(strValue);}string POp(const int cnt){string str;if (cnt < Count()){str = m_vecItem[cnt];}return str;}private:vector<string> m_vecItem;};int main(){ConcreteAggregate* pName = NULL;pName = new ConcreteAggregate();if (NULL != pName){pName->Push("hello");pName->Push("word");pName->Push("cxue");}Iterator* iter = new ConcreteIterator(pName);if (NULL != iter){string strItem = iter->First();while (!iter->IsEnd()){cout << iter->GetCur() << " is ok" << endl;iter->Next();}}delete iter;iter = NULL;system("pause");return 0;}

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