C++设计模式之迭代器模式

typedef struct tagNode
{
     int value;
     tagNode *pPre;
     tagNode *pNext;
}Node;
 
class CList
{
public:
     CList();
     CList(size_t n);
     ~CList();
 
     bool PushBack(int value);
     bool PopBack(int &value);
     bool Insert(int pos, int value);
     bool Delete(int pos);
     bool IsEmpty();
     int GetLength();
 
     void Print();
 
     // To iterate the list
     bool HasNext();
     int Next();
 
private:
     int m_iLength;
     Node *m_pCurrent;
     Node *m_pHead;
     Node *m_pTail;
};

#include <iostream>
using namespace std;
 
typedef struct tagNode
{
     int value;
     tagNode *pNext;
}Node;
 
class JTList
{
public:
     JTList() : m_pHead(NULL), m_pTail(NULL){};
     JTList(const JTList &);
     ~JTList();
     JTList &operator=(const JTList &);
 
     long GetCount() const;
     Node *Get(const long index) const;
     Node *First() const;
     Node *Last() const;
     bool Includes(const int &) const;
 
     void Append(const int &);
     void Remove(Node *pNode);
     void RemoveAll();
 
private:
     Node *m_pHead;
     Node *m_pTail;
     long m_lCount;
};
 
class Iterator
{
public:
     virtual void First() = 0;
     virtual void Next() = 0;
     virtual bool IsDone() const = 0;
     virtual Node *CurrentItem() const  = 0;
};
 
class JTListIterator : public Iterator
{
public:
     JTListIterator(JTList *pList) : m_pJTList(pList), m_pCurrent(NULL){}
 
     virtual void First();
     virtual void Next();
     virtual bool IsDone() const;
     virtual Node *CurrentItem() const;
 
private:
     JTList *m_pJTList;
     Node *m_pCurrent;
};
 
JTList::~JTList()
{
     Node *pCurrent = m_pHead;
     Node *pNextNode = NULL;
     while (pCurrent)
     {
          pNextNode = pCurrent->pNext;
          delete pCurrent;
          pCurrent = pNextNode;
     }
}
 
long JTList::GetCount()const
{
     return m_lCount;
}
 
Node *JTList::Get(const long index) const
{
     // The min index is 0, max index is count - 1
     if (index > m_lCount - 1 || index < 0)
     {
          return NULL;
     }
 
     int iPosTemp = 0;
     Node *pNodeTemp = m_pHead;
     while (pNodeTemp)
     {
          if (index == iPosTemp++)
          {
               return pNodeTemp;
          }
          pNodeTemp = pNodeTemp->pNext;
     }
     return NULL;
}
 
Node *JTList::First() const
{
     return m_pHead;
}
 
Node *JTList::Last() const
{
     return m_pTail;
}
 
bool JTList::Includes(const int &value) const
{
     Node *pNodeTemp = m_pHead;
     while (pNodeTemp)
     {
          if (value == pNodeTemp->value)
          {
               return true;
          }
          pNodeTemp = pNodeTemp->pNext;
     }
     return false;
}
 
void JTList::Append(const int &value)
{
     // Create the new node
     Node *pInsertNode = new Node;
     pInsertNode->value = value;
     pInsertNode->pNext = NULL;
 
     // This list is empty
     if (m_pHead == NULL)
     {
          m_pHead = m_pTail = pInsertNode;
     }
     else
     {
          m_pTail->pNext = pInsertNode;
          m_pTail = pInsertNode;
     }
     ++m_lCount;
}
 
void JTList::Remove(Node *pNode)
{
     if (pNode == NULL || m_pHead == NULL || m_pTail == NULL)
     {
          return;
     }
 
     if (pNode == m_pHead) // If the deleting node is head node
     {
          Node *pNewHead = m_pHead->pNext;
          m_pHead = pNewHead;
     }
     else
     {
          // To get the deleting node's previous node
          Node *pPreviousNode = NULL;
          Node *pCurrentNode = m_pHead;
          while (pCurrentNode)
          {
               pPreviousNode = pCurrentNode;
               pCurrentNode = pCurrentNode->pNext;
               if (pCurrentNode == pNode)
               {
                    break;
               }
          }
 
          // To get the deleting node's next node
          Node *pNextNode = pNode->pNext;
 
          // If pNextNode is NULL, it means the deleting node is the tail node, we should change the m_pTail pointer
          if (pNextNode == NULL)
          {
               m_pTail = pPreviousNode;
          }
 
          // Relink the list
          pPreviousNode->pNext = pNextNode;
     }
 
     // Delete the node
     delete pNode;
     pNode = NULL;
     --m_lCount;
}
 
void JTList::RemoveAll()
{
     delete this;
}
 
void JTListIterator::First()
{
     m_pCurrent = m_pJTList->First();
}
 
void JTListIterator::Next()
{
     m_pCurrent = m_pCurrent->pNext;
}
 
bool JTListIterator::IsDone() const
{
     return m_pCurrent == m_pJTList->Last()->pNext;
}
 
Node *JTListIterator::CurrentItem() const
{
     return m_pCurrent;
}
 
int main()
{
     JTList *pJTList = new JTList;
     pJTList->Append(10);
     pJTList->Append(20);
     pJTList->Append(30);
     pJTList->Append(40);
     pJTList->Append(50);
     pJTList->Append(60);
     pJTList->Append(70);
     pJTList->Append(80);
     pJTList->Append(90);
     pJTList->Append(100);
 
     Iterator *pIterator = new JTListIterator(pJTList);
 
     // Print the list by JTListIterator
     for (pIterator->First(); !pIterator->IsDone(); pIterator->Next())
     {
          cout<<pIterator->CurrentItem()->value<<"->";
     }
     cout<<"NULL"<<endl;
 
     // Test for removing
     Node *pDeleteNode = NULL;
     for (pIterator->First(); !pIterator->IsDone(); pIterator->Next())
     {
          pDeleteNode = pIterator->CurrentItem();
          if (pDeleteNode->value == 100)
          {
               pJTList->Remove(pDeleteNode);
               break;
          }
     }
 
     // Print the list by JTListIterator
     for (pIterator->First(); !pIterator->IsDone(); pIterator->Next())
     {
          cout<<pIterator->CurrentItem()->value<<"->";
     }
     cout<<"NULL"<<endl;
 
     delete pIterator;
     delete pJTList;
 
     return 0;
}

class AbstractJTList
{
public:
     virtual Iterator *GetIterator() const = 0;
};

Iterator *JTList::GetIterator() const
{
     return new JTListIterator(this);
}

Iterator *pIterator = pJTList->GetIterator();

class IteratorPtr
{
public:
     IteratorPtr(Iterator *pIterator) : m_pIterator(pIterator){}
     ~IteratorPtr() { delete m_pIterator; }
 
     Iterator *operator->(){ return m_pIterator; }
     Iterator &operator*() { return *m_pIterator; }
 
private:
     IteratorPtr(const IteratorPtr &);
     IteratorPtr &operator=(const IteratorPtr &);
     void *operator new(size_t size);
     void operator delete(void *);
 
private:
     Iterator *m_pIterator;
};

IteratorPtr pIterator(pJTList->GetIterator());