decouple that a bit more.

OpenRa.Game/Traits/Production.cs

@@ -46,8 +46,8 @@ namespace OpenRa.Game.Traits
 
 			Game.world.Add( newUnit );
 
-			if( self.traits.Contains<RenderWarFactory>() )
-				self.traits.Get<RenderWarFactory>().EjectUnit();
+			foreach (var t in self.traits.WithInterface<INotifyProduction>())
+				t.UnitProduced(self, newUnit);
 
 			return true;
 		}

OpenRa.Game/Traits/RenderBuildingWarFactory.cs

@@ -3,7 +3,7 @@ using OpenRa.Game.Graphics;
 
 namespace OpenRa.Game.Traits
 {
-	class RenderWarFactory : IRender, INotifyBuildComplete, INotifyDamage, ITick
+	class RenderWarFactory : IRender, INotifyBuildComplete, INotifyDamage, ITick, INotifyProduction
 	{
 		public Animation roof;
 		bool doneBuilding;
@@ -42,11 +42,6 @@ namespace OpenRa.Game.Traits
 			}
 		}
 
-		public void EjectUnit()
-		{
-			roof.PlayThen(prefix + "build-top", () => isOpen = true);
-		}
-
 		public void Damaged(Actor self, AttackInfo e)
 		{
 			if (!e.DamageStateChanged) return;
@@ -62,5 +57,10 @@ namespace OpenRa.Game.Traits
 					break;
 			}
 		}
+
+		public void UnitProduced(Actor self, Actor other)
+		{
+			roof.PlayThen(prefix + "build-top", () => isOpen = true);
+		}
 	}
 }

OpenRa.Game/Traits/TraitsInterfaces.cs

@@ -38,6 +38,7 @@ namespace OpenRa.Game.Traits
 	interface IRender { IEnumerable<Renderable> Render(Actor self); }
 	interface INotifyDamage { void Damaged(Actor self, AttackInfo e); }
 	interface INotifyBuildComplete { void BuildingComplete (Actor self); }
+	interface INotifyProduction { void UnitProduced(Actor self, Actor other); }
 	interface IOrder
 	{
 		Order IssueOrder( Actor self, int2 xy, MouseInput mi, Actor underCursor );