runtime error: Cannot modify

ID:2268339
 
Jul 11 2017, 6:59 am
(See the best response by Kaiochao.)
Code:
/obj/screen/hand/l_hand
    name="Left Hand"
    icon='icon/interface.dmi'
    icon_state="l_hand_inactive"
    New(client/c)
        screen_loc="3,1"
        c.screen+=src
    Click()
        if(activehand=="Left")
            return
        if(activehand=="Right") 
            handchecker_icon()      
/obj/screen/hand/r_hand
    name="Right Hand"
    icon='icon/interface.dmi'
    icon_state="r_hand_inactive"
    New(client/c)
        screen_loc="2,1"
        c.screen+=src
    Click()
        if(activehand=="Right")
            return
        if(activehand=="Left")  
            usr<<"test"
            handchecker_icon()
            return
/obj/screen/hand/proc/handchecker_icon()
    var/obj/screen/hand/r = /obj/screen/hand/r_hand/
    var/obj/screen/hand/l = /obj/screen/hand/l_hand/
    if(activehand="Right")
        r.icon_state="r_hand_active"
        l.icon_state="l_hand_inactive"
        return
    if(activehand="Left")
        r.icon_state="r_hand_inactive"
        l.icon_state="l_hand_active"
        return


the error
runtime error: Cannot modify /obj/screen/hand/r_hand.icon_state.
proc name: handchecker icon (/obj/screen/hand/proc/handchecker_icon)
  usr: Salazar Neck Twister (/mob/human)
  src: Left Hand (/obj/screen/hand/l_hand)
  usr.loc: Magi Turf (6,10,1) (/turf/floors/Magi_Turf)
  src.loc: null
  call stack:
Left Hand (/obj/screen/hand/l_hand): handchecker icon()
Left Hand (/obj/screen/hand/l_hand): Click(null, "mapwindow.map", "icon-x=16;icon-y=19;left=1;scr...")

Problem description: So it is supose to change the selected hand, and it is supose to indicate that by changing icon_states from inactive to active. But when i try to switch hands, i get this error. Any ideas on what im doing wrong
Jul 11 2017, 8:58 am
If it is failing to change the icon state, that is probably because the thing you are trying to change doesn't exist. Are you sure you have a valid reference to the object you are modifying an icon_state for?
Jul 11 2017, 9:47 am
In response to Foogimicester
So i think that is it, but how do i refer to it after the obj is created?
This is how it is created at the start.
    Login()
        new/obj/screen/hand/l_hand(src.client)
        new/obj/screen/hand/r_hand(src.client)
Jul 11 2017, 10:25 am
In response to Killerken924
Best response
When you do "new/type(...)", that doesn't just create an object, it also acts as a "reference" to the object that was created. So, you can stick it in a variable, like so:
mob/whatever
  // You can declare multiple variables like this to avoid repetition:
  var obj/screen/hand // this is part of the type of the variables
    l_hand/left_hand // this has the type /obj/screen/hand/l_hand and is named "left_hand"
    r_hand/right_hand // and similar here for the /.../r_hand 

  Login()
    // Instantiate the variables
    // You can leave out the type after "new" so it'll automatically
    // use the type that the variable is declared with
    left_hand = new(client)
    right_hand = new(client)

// Now, in your hanchecker_icon(), you can use usr.left_hand and usr.right_hand 
// to refer to these objects again.

The problem with your current code is that type paths aren't the same as the instantiated objects. You can have many objects of the same type, but the type itself isn't actually an object.