Iterator:
Provides a way to sequentially access aggregate objects without
exposing the
structure of the aggregate.
**Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
class Program
{
static void Main(string[] args)
{
ConcreteAggregate a = new ConcreteAggregate();
a[0] = "Item A";
a[1] = "Item B";
a[2] = "Item C";
ConcreteIterator i = new ConcreteIterator(a);
Console.WriteLine("Iterating over collection");
object item = i.First();
while (item != null)
{
Console.WriteLine(item);
item = i.Next();
}
Console.ReadKey();
}
}
abstract class Aggregate
{
public abstract Iterator CreateIterator();
}
class ConcreteAggregate : Aggregate
{
private ArrayList listItems = new ArrayList();
public override Iterator CreateIterator()
{
return new ConcreteIterator(this);
}
public int Count
{
get { return listItems.Count; }
}
public object this[int index]
{
get { return listItems[index]; }
set { listItems.Insert(index, value); }
}
}
abstract class Iterator
{
public abstract object Next();
public abstract object First();
public abstract bool isDone();
public abstract object CurrentItem();
}
class ConcreteIterator : Iterator
{
private ConcreteAggregate _aggregate;
private int current = 0;
public ConcreteIterator(ConcreteAggregate aggregate)
{
_aggregate = aggregate;
}
public override object Next()
{
object ret = null;
if (current < _aggregate.Count - 1)
ret = _aggregate[++current];
return ret;
}
public override object First()
{
return _aggregate[0];
}
public override bool isDone()
{
return current >= _aggregate.Count;
}
public override object CurrentItem()
{
return _aggregate[current];
}
}
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