206

Структура паттерна на языке C#

Классическое представление

class Program

{

static void Main()

{

Aggregate a = new ConcreteAggregate();

a[0] = "Element A"; a[1] = "Element B"; a[2] = "Element C"; a[3] = "Element D";

Iterator i = a.CreateIterator();

for (object e = i.First(); !i.IsDone(); e = i.Next()) Console.WriteLine(e);

}

}

abstract class Aggregate

{

public abstract Iterator CreateIterator(); public abstract int Count { get; }

public abstract object this[int index]

{

get; set;

}

}

abstract class Iterator

{

public abstract object First(); public abstract object Next(); public abstract bool IsDone();

public abstract object CurrentItem();

}

class ConcreteIterator : Iterator

{

private Aggregate aggregate; private int current = 0;

public ConcreteIterator(Aggregate aggregate)

{

this.aggregate = aggregate;

}

class ConcreteAggregate : Aggregate

{

private ArrayList items = new ArrayList();

public override Iterator CreateIterator()

{

return new ConcreteIterator(this);

}

public override int Count

{

get { return items.Count; }

}

public override object this[int index]

{

get { return items[index]; }

set { items.Insert(index, value); }

}

}

public override object First()

{

return aggregate[0];

}

public override object Next()

{

if (current++ < aggregate.Count - 1) return aggregate[current];

else

return null;

}

public override object CurrentItem()

{

return aggregate[current];

}

public override bool IsDone()

{

if (current < aggregate.Count) return false;

current = 0; return true;

}

}

См. Пример к главе: \016_Iterator\001_Iterator

207

Представление Microsoft .NET

class Program
{
static void Main()
{
Enumerable enumerable = new Enumerable();
enumerable[0]	= "Element A";
enumerable[1]	= "Element B";
enumerable[2]	= "Element C";
enumerable[3]	= "Element D";
foreach (var item in enumerable)
{
Console.WriteLine(item);
}
}
}
interface IEnumerable	interface IEnumerator
{	{
IEnumerator GetEnumerator();	bool MoveNext();
}	void Reset();
	object Current { get; }
	}
class Enumerable : IEnumerable	class Enumerator : IEnumerator
{	{
private ArrayList items = new ArrayList();	private Enumerable enumerable;
	private int current = -1;
public object this[int index]
{	public Enumerator(Enumerable enumerable)
get { return items[index]; }	{
set { items.Insert(index, value); }	this.enumerable = enumerable;
}	}
public int Count	// Реализация интерфейса IEnumerator.
{	public bool MoveNext()
get { return items.Count; }	{
}	if(current < enumerable.Count	- 1)
	{
// Реализация интерфейса IEnumerable.	current++;
public IEnumerator GetEnumerator()	return true;
{	}
return new Enumerator(this);	return false;
}	}
}
	public void Reset()
	{
	current = -1;
	}
	public object Current
	{
	get { return enumerable[current];		}
	}
	}

См. Пример к главе: \016_Iterator\003_Enumerator