Organizing aliens in a shmup

Type Alien

   Global List:TList = CreateList()
   
   Field _Link:TLink

   Function Create()
      Local A:Alien
      A = New Alien
      A._Link = List.AddLast(A)
   End Function

   Function UpdateAll()
      Local A:Alien

      For A = EachIn List
         A.Update()
      Next
   End Function

   Method Update()
   End Method
   
   Method Free()
      _Link.Remove()
      _Link = Null
   End Method

End Type

Just Alien.Create() to create an alien, call Alien.UpdateAll() in your main loop, and that will call the Update() function for each alien, inside which you can access the fields of the type. And when the alien is destroyed just call Free() or Self.Free() in its update function, or with the pointer to it if freeing it from somewhere else.