Runtime error

ID:1728035
 
Nov 26 2014, 2:35 pm
(See the best response by Neimo.)
Code:
Crossed(A)
    if(istype(A,/mob))
        var/mob/O=owner
        var/mob/D=A
        if(O.aff==D.aff)return
        D.snared(15*O.tier51,3)
    if(istype(A,/obj))
        var/obj/T = A
        if(T.density)
            T.loc=loc


I get the following runtime error:

runtime error: Cannot read null.aff
proc name: Crossed (/obj/staticfield/Crossed)
source file: Copy Ninja Jutsus.dm,84
usr: JonJon (/mob/player)
src: the staticfield (/obj/staticfield)
call stack:

"aff" is a mob/var initialized to 0. I don't know why it's saying it's null. And I'm not certain why I'm getting this error.

Nov 26 2014, 2:42 pm
Best response
Either O or D is null, that's what the error means.
Nov 26 2014, 2:43 pm
I don't see how either of them could be null
Nov 26 2014, 2:46 pm
 
if(o)
    world << "o exists"
else
    world << "o does not exist"

See what happens! Add it underneath the variable referencing and above the if() statement.
Nov 26 2014, 2:49 pm (Edited on Nov 26 2014, 2:54 pm)
Oh, obj/var/owner is set to null. What would be a better way to initialize it? owner is set to whoever makes the obj

Also, the results were:

o exists
o exists
o exists
o does not exist
o does not exist
o does not exist
o exists
o exists
Nov 26 2014, 9:14 pm
The default value of the owner variable doesn't really matter in this case.

obj
    Lightning
        New(location, caster)
            ..()
            src.loc = location
            src.owner = caster

        Crossed(A)
            if(istype(A, /mob))
                var/mob/O = owner
                var/mob/D = A
                world << "[O] [O.aff], [A] [D] [D.aff]"
                if(O.aff == D.aff)
                    world << "return"
                    return
                D.snared(15 * O.tier51, 3)
            if(istype(A,/obj))
                var/obj/T = A
                if(T.density)
                    T.loc = loc

mob
    verb
        CreateLightning()
            new/obj/Lightning(src.loc, src)


I tried it with that and it worked fine. Not sure why it's giving you an error.
Nov 27 2014, 5:22 am
It's a little confusing why only some of the times O is not set to null. The logic works fine, I just don't know why I'm getting the error
Nov 27 2014, 7:37 am
Could you post the code for the entire technique? It would be a lot easier to pinpoint it that way.