Komponemts

code/datums/components/container_item/container_item.dm

@@ -0,0 +1,10 @@
+/// Container item, an item which can be stored by specialized containers.
+/datum/component/container_item
+
+/datum/component/container_item/Initialize()
+	. = ..()
+	RegisterSignal(parent, COMSIG_CONTAINER_TRY_ATTACH, .proc/try_attach)
+
+/// Called when parent is added to the container.
+/datum/component/container_item/proc/try_attach(datum/source, atom/container, mob/user)
+	return FALSE

code/datums/components/container_item/tank_holder.dm

@@ -0,0 +1,31 @@
+/// Tank holder item - Added to an object which can be added to a tank holder.
+/datum/component/container_item/tank_holder
+	var/tank_holder_icon_state
+	var/make_density
+
+/datum/component/container_item/tank_holder/Initialize(state, density = TRUE)
+	if(!isitem(parent))
+		return COMPONENT_INCOMPATIBLE
+
+	tank_holder_icon_state = state
+	make_density = density
+	return ..()
+
+/datum/component/container_item/tank_holder/try_attach(datum/source, obj/structure/tank_holder/container, mob/user)
+	if(!container || !istype(container))
+		return FALSE
+	var/obj/item/I = parent
+	if(container.contents.len)
+		if(user)
+			to_chat(user, "<span class='warning'>There's already something in [container].</span>")
+		return TRUE
+	if(user)
+		if(!user.transferItemToLoc(I, container))
+			return TRUE
+		to_chat(user, "<span class='notice'>You put [I] into [container].</span>")
+	else
+		I.forceMove(container)
+	container.tank = I
+	container.density = make_density
+	container.icon_state = tank_holder_icon_state
+	return TRUE