Iterate

// Totorial on https://indiedevart.wordpress.com/


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication9
{
    class Program
    {
        static void Main(string[] args)
        {
            Aggregate aggr = new Aggregate();

            aggr[0] = 7;
            aggr[1] = 8;
            aggr[2] = 9;
            aggr[3] = 89;

            IIterator iter = aggr.GetIterator();

            for (int i = iter.FirstItem; iter.IsDone == false; i = iter.NextItem)
            {
                Console.WriteLine(i.ToString());
            }
            Console.ReadLine();
        }
    }
    interface IIterator
    {
        int FirstItem { get; }
        int NextItem { get; }
        int CurrentItem { get; }
        bool IsDone { get; }
    }

    class Iterator : IIterator
    {
        IAggregate aggregate = null;
        int currentIndex = 0;

        public Iterator(IAggregate newAggregate)
        {
            aggregate = newAggregate;
        }

        public int FirstItem
        {
            get
            {
                currentIndex = 0;
                return aggregate[currentIndex];
            }
        }

        public int NextItem
        {
            get
            {
                currentIndex += 1;

                if (IsDone == false)
                {
                    return aggregate[currentIndex];
                }
                else
                {
                    return -1;
                }
            }
        }

        public int CurrentItem
        {
            get
            {
                return aggregate[currentIndex];
            }
        }

        public bool IsDone
        {
            get
            {
                if (currentIndex < aggregate.Count)
                {
                    return false;
                }
                return true;
            }
        }

    }

    interface IAggregate
    {
        IIterator GetIterator();
        int this[int itemIndex] { set; get; }
        int Count { get; }
    }

    class Aggregate : IAggregate
    {
        List<int> values = null;

        public Aggregate()
        {
            values = new List<int>();
        }



        public IIterator GetIterator()
        {
            return new Iterator(this);
        }



        public int this[int itemIndex]
        {
            get
            {
                if (itemIndex < values.Count)
                {
                    return values[itemIndex];
                }
                else
                {
                    return -1;
                }
            }
            set
            {
                values.Add(value);
            }
        }

        public int Count
        {
            get
            {
                return values.Count;
            }
        }
    }
}