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迭代器模式

定义：提供一种方法顺序访问一个集合对象中的元素，但是又不暴露该对象的内部显示

这里采用了类模板来定义类，强化对模板的运用。

代码：

#include 
   
    #include 
    
     #include 
     
      using namespace std;//抽象迭代器类template
      
       class Iterator{public:	virtual T firstItem() = 0;	virtual T nextItem() = 0;	virtual T currentItem() = 0;	virtual bool isEnd() = 0;};//抽象聚合类template
       
        class Aggregate{public:	virtual int count() = 0;	virtual void pushItem(const T& str) = 0;	virtual T removeItem(const int index) = 0;	virtual Iterator
        
         * createIterator() = 0;};//具体聚合类template
         
          class ConcreteAggregate :Aggregate
          
           {public: ConcreteAggregate() :m_pIter(nullptr){} ~ConcreteAggregate() { if (m_pIter) { delete m_pIter; m_pIter = nullptr; } } int count() { return m_listItem.size(); } void pushItem(const T& str) { m_listItem.push_back(str); } T removeItem(const int index) { T res; if (index < count()) { res = m_listItem[index]; } return res; } Iterator
           
            * createIterator() { m_pIter = new ConcreteIterator
            
             (this); return m_pIter; }private: vector
             
               m_listItem; Iterator
              
                *m_pIter;};//具体迭代器类template
               
                class ConcreteIterator :public Iterator
                
                 {public: ConcreteIterator(Aggregate
                 
                  * pA) :m_cnt(0), m_pConcreteA(nullptr) { m_pConcreteA = pA; } T firstItem() { return m_pConcreteA->removeItem(0); } T nextItem() { m_cnt++; if (m_cnt < m_pConcreteA->count()) { return m_pConcreteA->removeItem(m_cnt); } return T(); } T currentItem() { return m_pConcreteA->removeItem(m_cnt); } bool isEnd() { return ((m_cnt >= m_pConcreteA->count()) ? true : false); }private: Aggregate
                  
                    *m_pConcreteA; int m_cnt;};//客户端int main(){ ConcreteAggregate
                   
                     *p = new ConcreteAggregate < string > ; p->pushItem("宫保鸡丁"); p->pushItem("鱼香肉丝"); p->pushItem("翡翠白菜"); p->pushItem("青椒牛肉"); Iterator
                    
                      *it = p->createIterator(); if (it) { string item = it->firstItem(); cout << "胖虎今天要吃的是菜是" << endl; while (!it->isEnd()) { cout << it->currentItem().c_str() << endl; it->nextItem(); } } cout << "====================" << endl; ConcreteAggregate
                     
                       *p1 = new ConcreteAggregate
                      
                       ; p1->pushItem(999); p1->pushItem(888); p1->pushItem(666); p1->pushItem(555); Iterator
                       
                         *pIter = p1->createIterator(); if (pIter) { int item = pIter->firstItem(); cout << "小明今天要学习的数字是" << endl; while (!pIter->isEnd()) { cout << pIter->currentItem() << endl; pIter->nextItem(); } } if (p) { delete p; p = nullptr; } if (p1) { delete p1; p1 = nullptr; } return 0;}
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     
    
   

效果：

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