void add(IInputKeyReceiver re)
 {
     if (receiverArray.Length == tail)
     {
         Array.Resize(ref receiverArray, checked (tail * 2));
     }
     receiverArray[tail++] = re;
 }
 /// <summary>
 /// 指定した Updatable を Update 対象から除外する.
 /// </summary>
 public static void Remove(IInputKeyReceiver updatable)
 {
     if (updatable == null)
     {
         return;
     }
     sender.remove(updatable);
 }
 /// <summary>
 /// Update 対象の追加.
 /// </summary>
 public static void Add(IInputKeyReceiver re)
 {
     if (re == null)
     {
         return;
     }
     sender.add(re);
 }
 void remove(IInputKeyReceiver updatable)
 {
     for (int i = 0; i < receiverArray.Length; i++)
     {
         if (receiverArray[i] == updatable)
         {
             receiverArray[i] = null;
             refreshUpdatableArray();
             return;
         }
     }
 }