迭代器模式

迭代器模式, 提供一种方法顺序访问一个聚合对象中各个元素, 而又不暴露该对象的内部表示.

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abstract class Iterator {
public abstract object First();
public abstract object Next();
public abstract bool IsDone();
public abstract object CurrentItem();
}
abstract classs Aggregate {
public abstract Iterator CreateIterator();
}
class ConcreteTerator : Iterator {
private ConcreteAggregate aggregate;
private int current = 0;
public ConcreteIterator(ConcreteAggregate aggregate) {
this.aggregate = aggregate;
}
public override object First() {
return aggregate[0];
}
public override object Next() {
object ret = null;
current++;
if(current < aggregate.Count) {
ret = aggregate[current];
}
retrun ret;
}
public override bool IsDone() {
return current >= aggregate.Count;
}
public override object CurrentItem() {
return aggregate[current];
}
}
class ConcreteAggregate : Aggregate {
private IList<object> items = new IList<Object>();
public override Iterator CreateIterator() {
return new ConcreteIterator(this);
}
public int Count {
get {
return items.Count;
}
}
public object this[int index] {
get {
return items[index];
}
set {
items.insert(index, value);
}
}
}