Iterator（迭代器）

  1 #include <iostream>
  2 #include <string>
  3 #include <vector>
  4 using namespace std;
  5 
  6 //抽象迭代角色：该角色负责定义访问和遍历元素的接口。
  7 class Iterator
  8 {
  9 public:
 10     Iterator(){}
 11     virtual ~Iterator(){};
 12     virtual string First() = 0;
 13     virtual string Next() = 0;
 14     virtual string GetCur() = 0;
 15     virtual bool IsEnd() = 0;
 16 };
 17 
 18 //抽象聚合角色：该角色提供创建迭代器角色的接口。
 19 class Aggregate
 20 {
 21 public:
 22     virtual int Count() = 0;
 23     virtual void Push(const string &strValue) = 0;
 24     virtual string POp(const int cnt) = 0;
 25 };
 26 
 27 //具体迭代角色：该角色实现Iterator接口，完成容器元素的遍历。
 28 class ConcreteIterator : public Iterator
 29 {
 30 public:
 31     ConcreteIterator(Aggregate *p_aggregate):m_aggregate(p_aggregate),m_cnt(0){}
 32 
 33     string First()
 34     {
 35         return m_aggregate->POp(0);
 36     }
 37 
 38     string Next()
 39     {
 40         string str;
 41         m_cnt++;
 42         if (m_cnt < m_aggregate->Count())
 43         {
 44             str = m_aggregate->POp(m_cnt);
 45         }
 46 
 47         return str;
 48     }
 49 
 50     string GetCur()
 51     {
 52         return m_aggregate->POp(m_cnt);
 53     }
 54 
 55     bool IsEnd()
 56     {
 57         return m_cnt >= m_aggregate->Count() ? true : false;
 58     }
 59 
 60     ~ConcreteIterator(){ }
 61 
 62 private:
 63     Aggregate *m_aggregate;
 64     int m_cnt;
 65 };
 66 
 67 //具体聚集角色：该角色实现抽象聚集接口，创建出容纳迭代器的对象
 68 class ConcreteAggregate : public Aggregate
 69 {
 70 public:
 71     ConcreteAggregate()
 72     {
 73         m_vecItem.clear();
 74     }
 75 
 76     ~ConcreteAggregate()
 77     {
 78     }
 79 
 80     int Count()
 81     {
 82         return m_vecItem.size();
 83     }
 84 
 85     void Push(const string &strValue)
 86     {
 87         m_vecItem.push_back(strValue);
 88     }
 89 
 90     string POp(const int cnt)
 91     {
 92         string str;
 93         if (cnt < Count())
 94         {
 95             str = m_vecItem[cnt];
 96         }
 97         return str;
 98     }
 99 
100 private:
101     vector<string> m_vecItem;
102 };
103 
104 int main()
105 {
106     ConcreteAggregate* pName = NULL;
107     pName = new ConcreteAggregate();
108     if (NULL != pName)
109     {
110         pName->Push("hello");
111         pName->Push("word");
112         pName->Push("cxue");
113     }
114 
115     Iterator* iter = new ConcreteIterator(pName);
116 
117     if (NULL != iter)
118     {
119         string strItem = iter->First();
120         while (!iter->IsEnd())
121         {
122             cout << iter->GetCur() << " is ok" << endl;
123             iter->Next();
124         }
125     }
126 
127     delete iter;
128     iter = NULL;
129 
130     system("pause");
131 
132     return 0;
133 }