迭代器iterator在程序到底起什么作用？ |YEYUANGEN
1.类似于一个指针，但不是指针2.在container中相当于指向element的指针，但其实现并不是指针，而是对象。
3.从大的方面讲是容器和算法之间的黏合剂
从小的方面讲是类似智能指针的东东
试一下copy算法来加深理解
:)
4.iterator相当于一个container的指针类型，可以定义一个对象对container中的每个元素进行连续的访问。
5.你看一下源代码很快就明白了。我原来也晕了半天，实际就是指针，通过typedef实现。
template <class
T> class XXX
{
...
...
typedef T*
iterator
typedef const T* const_iterator;
};
建议：看C++ primer加深理解
源码参考：
实现:
1)Iterator.h
#ifndef ITERATOR_H
#define ITERATOR_H
typedef int DATA;
class Iterater;
// 容器的抽象基类
class Aggregate
{
public:
virtual ~Aggregate(){}
virtual Iterater* CreateIterater(Aggregate *pAggregate) = 0;
virtual int GetSize() = 0;
virtual DATA GetItem(int nIndex) = 0;
};
// 迭代器的抽象基类
class Iterater
{
public:
virtual ~Iterater(){}
virtual void First() = 0;
virtual void Next() = 0;
virtual bool IsDone() = 0;
virtual DATA CurrentItem() = 0;
private:
};
// 一个具体的容器类,这里是用数组表示
class ConcreateAggregate
: public Aggregate
{
public:
ConcreateAggregate(int nSize);
virtual ~ConcreateAggregate();
virtual Iterater* CreateIterater(Aggregate *pAggregate);
virtual int GetSize();
virtual DATA GetItem(int nIndex);
private:
int m_nSize;
DATA *m_pData;
};
// 访问ConcreateAggregate容器类的迭代器类
class ConcreateIterater
: public Iterater
{
public:
ConcreateIterater(Aggregate* pAggregate);
virtual ~ConcreateIterater(){}
virtual void First();
virtual void Next();
virtual bool IsDone();
virtual DATA CurrentItem();
private:
Aggregate*m_pConcreateAggregate;
int m_nIndex;
};
#endif
复制代码
2)Iterator.cpp
#include <iostream>
#include "Iterator.h"
ConcreateAggregate::ConcreateAggregate(int nSize)
: m_nSize(nSize)
, m_pData(NULL)
{
m_pData = new DATA;
for (int i = 0; i < nSize; ++i)
{
m_pData = i;
}
}
ConcreateAggregate::~ConcreateAggregate()
{
delete [] m_pData;
m_pData = NULL;
}
Iterater* ConcreateAggregate::CreateIterater(Aggregate *pAggregate)
{
return new ConcreateIterater(this);
}
int ConcreateAggregate::GetSize()
{
return m_nSize;
}
DATA ConcreateAggregate::GetItem(int nIndex)
{
if (nIndex < m_nSize)
{
return m_pData;
}
else
{
return -1;
}
}
ConcreateIterater::ConcreateIterater(Aggregate* pAggregate)
: m_pConcreateAggregate(pAggregate)
, m_nIndex(0)
{
}
void ConcreateIterater::First()
{
m_nIndex = 0;
}
void ConcreateIterater::Next()
{
if (m_nIndex < m_pConcreateAggregate->GetSize())
{
++m_nIndex;
}
}
bool ConcreateIterater::IsDone()
{
return m_nIndex == m_pConcreateAggregate->GetSize();
}
DATA ConcreateIterater::CurrentItem()
{
return m_pConcreateAggregate->GetItem(m_nIndex);
}
//复制代码
3_Main.cpp
#include "Iterator.h"
#include <iostream>
int main()
{
Aggregate* pAggregate = new ConcreateAggregate(4);
Iterater*pIterater= new ConcreateIterater(pAggregate);
for (; false == pIterater->IsDone(); pIterater->Next())
{
std::cout << pIterater->CurrentItem() << std::endl;
}
return 0;
}复制代码
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