using System;
using System.Collections;
namespace DoFactory.GangOfFour.Iterator.RealWorld
{
/// <summary>
/// MainApp startup class for Real-World
/// Iterator Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
static void Main()
{
// Build a collection
Collection collection = new Collection();
collection[0] = new Item("Item 0");
collection[1] = new Item("Item 1");
collection[2] = new Item("Item 2");
collection[3] = new Item("Item 3");
collection[4] = new Item("Item 4");
collection[5] = new Item("Item 5");
collection[6] = new Item("Item 6");
collection[7] = new Item("Item 7");
collection[8] = new Item("Item 8");
// Create iterator
Iterator iterator = new Iterator(collection);
// Skip every other item
iterator.Step = 2;
Console.WriteLine("Iterating over collection:");
for (Item item = iterator.First();
!iterator.IsDone; item = iterator.Next())
{
Console.WriteLine(item.Name);
}
// Wait for user
Console.ReadKey();
}
}
/// <summary>
/// A collection item
/// </summary>
class Item
{
private string _name;
// Constructor
public Item(string name)
{
this._name = name;
}
// Gets name
public string Name
{
get { return _name; }
}
}
/// <summary>
/// The 'Aggregate' interface
/// </summary>
interface IAbstractCollection
{
Iterator CreateIterator();
}
/// <summary>
/// The 'ConcreteAggregate' class
/// </summary>
class Collection : IAbstractCollection
{
private ArrayList _items = new ArrayList();
public Iterator CreateIterator()
{
return new Iterator(this);
}
// Gets item count
public int Count
{
get { return _items.Count; }
}
// Indexer
public object this[int index]
{
get { return _items[index]; }
set { _items.Add(value); }
}
}
/// <summary>
/// The 'Iterator' interface
/// </summary>
interface IAbstractIterator
{
Item First();
Item Next();
bool IsDone { get; }
Item CurrentItem { get; }
}
/// <summary>
/// The 'ConcreteIterator' class
/// </summary>
class Iterator : IAbstractIterator
{
private Collection _collection;
private int _current = 0;
private int _step = 1;
// Constructor
public Iterator(Collection collection)
{
this._collection = collection;
}
// Gets first item
public Item First()
{
_current = 0;
return _collection[_current] as Item;
}
// Gets next item
public Item Next()
{
_current += _step;
if (!IsDone)
return _collection[_current] as Item;
else
return null;
}
// Gets or sets stepsize
public int Step
{
get { return _step; }
set { _step = value; }
}
// Gets current iterator item
public Item CurrentItem
{
get { return _collection[_current] as Item; }
}
// Gets whether iteration is complete
public bool IsDone
{
get { return _current >= _collection.Count; }
}
}
}