Runtime Error =/

ID:141516
 
Feb 11 2009, 9:44 am
Code:
L.spelldelay=1
                var/list/J[1]
                var/C = 1
                var/mob/enemies/M
                for(M as mob in oview(5))
                    if (istype(M,/mob/enemies))
                        J[C] = M
                        C++
                        J.len++
                if(J[1]!=null)
                    MP -= round(14*sqrt(poisonlevel),1)
                    M = J[1]
                    missile(/obj/spells/poisonbolt,usr,M)
                    sleep(get_dist(usr,M))
                    M.overlays += /obj/spells/poison
                    var/D = round(4+(poisonlevel/2),1)
                    while(D>0)
                        var/damage = round( rand(10*(sqrt(poisonlevel*((Intelligence/100)+1))),13*(sqrt(poisonlevel*((Intelligence/100)+1)))) , 1)
                        if (M.poiswk>0)
                            damage = round(damage*(1+(M.poiswk/100)),1)
                        if (M.poisres>0)
                            damage -= round(damage*(M.poisres/100),1)
                        M.HP -= damage
                        s_damage(M, damage, "green")
                        sleep(10)
                        DeadEnemy(M)
                        D--


Problem description: Whenever i use the spell, and a monster dies, i get a runtime error with anything thats under "while(D>0)" and the runtime error says "runtime error: Cannot read null.poiswk" and its not just the poiswk, i tried taking that out, and it still had the same error but with poisres and so on....
Feb 11 2009, 9:54 am
The cause is pretty obvious, and its a symptom of not exactly understanding what you're doing/lists and so not being aware what the effect of your code precisely is. The error means M is set to null at the time the code accessing those vars executes.
Feb 11 2009, 9:58 am
In response to Kaioken
Well, what makes no sense, is that that's the ONLY spell i get that error with, the other spells work just fine, and they have the same vars just that they're not the poison vars.
Feb 11 2009, 10:39 am
In response to Yamikaiba1236
Every time you sleep() you're naturally not executing statements one after another instantly; there is therefore a space for other functions to execute and for things to happen - which includes any object you may be messing with being potentially deleted. Especially if the current proc can do the deletion.