23种设计模式C++实例之迭代器模式

#include <iostream>

using namespace std;

/*
* 迭代器模式
* */

typedef int Object;
#define SIZE 5

class Iterator {
public:
virtual ~Iterator() {}
virtual void first() = 0;
virtual void next() = 0;
virtual bool end() = 0;
virtual Object curItem() = 0;
};

class Aggregate {
public:
virtual ~Aggregate() {}
virtual Iterator* createIterator() = 0;
virtual Object getItem(int index) = 0;
virtual int getSize() = 0;
};

class ConcreteIterator: public Iterator {
public:
ConcreteIterator(Aggregate *ag) {
this->ag = ag;
index = 0;
}
virtual void first() {
index = 0;
}
virtual void next() {
if (index < ag->getSize()) {
index++;
}
}
virtual bool end() {
return (index == ag->getSize());
}
Object curItem() {
return ag->getItem(index);
}
private:
int index;
Aggregate* ag;
};

class ConcreteAggregate: public Aggregate {
public:
ConcreteAggregate() {
for(int i = 0; i < SIZE; ++i) {
object[i] = i + 1;
}
}
virtual Iterator* createIterator() {
return new ConcreteIterator(this);
}
virtual Object getItem(int index) {
return object[index];
}
virtual int getSize() {
return SIZE;
}
private:
Object object[SIZE];
};

int main() {
Aggregate* ag = new ConcreteAggregate;
Iterator* it = ag->createIterator();
for (;!(it->end()); it->next()) {
cout << it->curItem() << endl;
}
delete ag;
delete it;
return 0;
}