01.概念
02.角色和职责
- 提供一种方法顺序访问一个聚敛对象的各个元素,而又不暴露该对象的内部表示。
- 为遍历不同的聚集结构提供如开始,下一个,是否结束,当前一项等统一接口。
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03.代码案例
#include <iostream>
using namespace std;
typedef int Object;
#define SIZE 5
class MyIterator
{
public:
virtual void First() = 0;
virtual void Next() = 0;
virtual bool IsDone() = 0;
virtual Object CurrentItem() = 0;
private:
};
class Aggregate
{
public:
virtual Object getItem(int index) = 0;
virtual MyIterator* CreateIterator() = 0;
virtual int getSize() = 0;
private:
};
class Contretelterator : public MyIterator
{
public:
Contretelterator(Aggregate* ag)
{
_ag = ag;
_idx = 0;
}
~Contretelterator()
{
_ag = NULL;
_idx = 0;
}
virtual void First()
{
_idx = 0;
}
virtual void Next()
{
if (_idx < _ag->getSize())
{
_idx++;
}
}
virtual bool IsDone()
{
return (_idx == _ag->getSize());
}
virtual Object CurrentItem()
{
return _ag->getItem(_idx);
}
private:
int _idx;
Aggregate* _ag;
};
class ConcreteAggregate : public Aggregate
{
public:
ConcreteAggregate()
{
for (int i = 0; i < SIZE; i++)
{
object[i] = i + 1;
}
}
~ConcreteAggregate()
{
}
virtual Object getItem(int index)
{
return object[index];
}
virtual MyIterator* CreateIterator()
{
return new Contretelterator(this);
}
virtual int getSize()
{
return SIZE;
}
private:
Object object[SIZE];
};
void main()
{
//创建一个集合
Aggregate* ag = new ConcreteAggregate();
//创建一个遍历这个集合的 迭代器
MyIterator* it = ag->CreateIterator();
//通过迭代器遍历集合
for (it->First(); !(it->IsDone()); it->Next())
{
cout << it->CurrentItem() << " ";
}
delete it;
delete ag;
}
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