迭代器模式
Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
(它提供一种方法访问一个容器对象中各个元素,而又不需暴露该对象的内部细节。)
通用类图
抽象迭代器类，定义访问和遍历元素的接口
具体迭代器类，继承抽象迭代器类，实现接口方法，与具体容器类关联
抽象容器类，提供创建具体迭代器的接口
具体容器类，继承抽象容器类，实现方法，创建初容纳迭代器的对象，使用具体迭代器类
通用源码
//抽象迭代器类
template <typename T>
class Iterator {
public:
virtual T next() = 0;
virtual booleam remove() = 0;
virtual booleam hasxNext() = 0;
};
//具体迭代器类
template <typename T>
class ConcreteIterator: public Iterator {
public:
ConcreteIterator(vector<T> v): vt(v) { }
booleam hasxNext() {
if(cursor == vt.size()) return false;
else return true;
}
T next() {
T t;
if(hasxNext()) t = vt[cursor++];
return t;
}
booleam remove() {
vt.erase(vt.begin()+cursor++);
return true;
}
private:
vector<T> vt;
int cursor = 0;
};
//抽象容器类
template <typename T>
class Aggregate {
public:
virtual void add(T) = 0;
virtual void remove(T) = 0;
virtual Iterator* iterator() = 0;
};
//具体容器类
template <typename T>
class ConcreteAggregate: public Aggregate {
public:
void add(T t) {
vt.insert(t);
}
void remove(T t) {
auto iter = find(vt.begin(), vt.end(), t);
vt.erase(iter);
}
Iterator* iterator() {
return new ConcreteIterator(vt);
}
private:
vector<T> vt;
};
应用
迭代器模式已经被各种容器已经内部实现了，这里讲述的是迭代器的内部大概是怎么实现的，它的思想是如何。
在一般的开发中，不需要自己再次实现迭代器模式
示例代码
#include <iostream>
#include <string>
using namespace std;
class IProject {
public:
virtual string getProjectInfo() = 0;
};
class Project : public IProject {
public:
Project(string s, int n, int c): name(s), num(n), cost(c) { }
string getProjectInfo() {
string info;
info = "name: " + name;
info += "\tnumber: " + to_string(num);
info += "\tcost: " + to_string(cost);
return info;
}
private:
string name;
int num;
int cost;
};
int main() {
IProject* p = new Project("2048", 2, 5000);
cout << p->getProjectInfo() << endl;
return 0;
}
