设计模式[8]-Iterator

Type: Behavioral

Iterator：提供一个方法连续访问一个聚合对象的元素，同时不暴露其底层表示

#include <iostream>
using namespace std;
#define Data int
class Iterator
{
public:
    virtual Data* next()=0;
};  

class ConcreteIterator: public Iterator
{
public:
    ConcreteIterator(Data* data, int* size)
    {
        m_pData = data;
        m_pSize = size;
        mIndex = 0;
    };
    Data* next()
    {
        if(m_pData != NULL && mIndex < *m_pSize){
            return &m_pData[mIndex++];
        } else {
            return NULL;
        }
    };
private:
    int mIndex;
    Data* m_pData;
    int* m_pSize;
};  

class Aggregate
{
public:
    virtual Iterator* createIterator() = 0;
};  

class ConcreteAggregate: public Aggregate
{
public:
    ConcreteAggregate(int size)
    {
        mSize = size;
        mData = new Data[size];
        for(int i=0;i<size; i++)
            mData[i] = i;
    };
    Iterator* createIterator()
    {
        Iterator* iterator = new ConcreteIterator(this->mData, &this->mSize);
        return iterator;
    };
private:
    Data* mData;
    int mSize;
};  

int main()
{
    Aggregate* pAggregate = new ConcreteAggregate(4);
    Iterator*  pIterator  = pAggregate->createIterator();  

    Data* data;
    int count = 0;
    while (data = pIterator->next())
    {
        if(count ++ > 10)
            break;
        cout <<*data<<endl;
    }
    system("pause");
    return 0;
}