Adding item to contents that already exists in contents doesn't give multiples <Solved>

ID:1190917
 
Mar 8 2013, 6:46 am (Edited on Mar 8 2013, 9:15 am)
(See the best response by Ter13.)
Code:
mob
    Player
        verb
            craftAccept()
                if(winget(usr, "craft", "is-visible")=="true")
                    if(usr.selectedRecipe)
                        //First check for present tools
                        var/AnvilPresent, FurnacePresent = 0
                        for(var/obj/t in oview(1))
                            if(t.name=="Anvil")
                                AnvilPresent=1
                            else if(t.name=="Furnace")
                                FurnacePresent=1
                        if(AnvilPresent>=usr.selectedRecipe.AnvilReq && FurnacePresent>=usr.selectedRecipe.FurnaceReq) //If the required equipment is present, continue
                            if(includeIngreds(usr.contents,usr.selectedRecipe.Ingredients)==0)
                                removeIgreds(usr.contents,usr.selectedRecipe.Ingredients)
                                for(var/obj/result in usr.selectedRecipe.Results)
                                    if(istype(result,/obj/Crafting))
                                        var/obj/Crafting/existingResult=typeFind(result,usr.contents)
                                        if(existingResult)
                                            var/obj/Crafting/p = result
                                            existingResult.Quantity+=p.Quantity
                                        else
                                            usr.contents+=result
                                    else
                                        usr.contents+=result

obj
    Recipe
        Equipment
            var/Slot
            HelmMk1
                name="Iron Helmet"
                icon='HelmMark1.dmi'
                icon_state=""
                FurnaceReq=1
                AnvilReq=1
                New()
                    var/obj/Crafting/RawMats/Metals/Iron/a1 = new()
                    a1.Quantity=1
                    src.Ingredients+=a1
                    var/obj/Equipment/Armour/Headwear/HelmMark1/a2 = new()
                    src.Results+=a2


Problem description:
If I craft a HelmMark1 then Iron is taken from my inventory and a Helm is added, as intended. If I do it again the Iron is removed once more, but a second Helm is not added.

However, if I do this with types of /obj/Crafting the intended Quantity is added to the existing item, as intended.
Mar 8 2013, 8:15 am
Best response
That's because you are adding a reference to an existing object. You need to instantiate a new copy of the existing item:

usr.contents += new result.type()
Mar 8 2013, 8:41 am
You know I have always wondered about how to do that. Thank you so much!