SoACompositeProxy

using System.Collections;
using System.Collections.Generic;

namespace DotNetDesignPatternDemos.Structural.Proxy
{
  class Creature
  {
    public byte Age;
    public int X, Y;
  }

  class Creatures
  {
    private readonly int size;
    private byte [] age;
    private int[] x, y;

    public Creatures(int size)
    {
      this.size = size;
      age = new byte[size];
      x = new int[size];
      y = new int[size];
    }

    public struct CreatureProxy
    {
      private readonly Creatures creatures;
      private readonly int index;

      public CreatureProxy(Creatures creatures, int index)
      {
        this.creatures = creatures;
        this.index = index;
      }

      public ref byte Age => ref creatures.age[index];
      public ref int X => ref creatures.x[index];
      public ref int Y => ref creatures.y[index];
    }

    public IEnumerator<CreatureProxy> GetEnumerator()
    {
      for (int pos = 0; pos < size; ++pos)
        yield return new CreatureProxy(this, pos);
    }
  }
  
  public class SoACompositeProxy
  {
    public static void Main(string[] args)
    {
      var creatures = new Creature[100];
      foreach (var c in creatures)
      {
        c.X++; // not memory-efficient
      }
      
      var creatures2 = new Creatures(100);
      foreach (var c in creatures2)
      {
        c.X++;
      }
    }
  }
}