Players cannot load in Developer Help

ID:139127
 
Jun 20 2011, 6:02 pm (Edited on Jun 20 2011, 6:15 pm)
Code:
mob
    proc
        load()
            if(fexists("savespot/[usr.key]"))
                if(usr.client)
                    var/savefile/load
                    load = new ("savespot/[usr.key]")
                    load["mob"] >> usr
                    load["x"] >> usr.x
                    load["y"] >> usr.y
                    load["z"] >> usr.z


Problem description:

It seems completely random that a mob bugs out and cannot be loaded, runtime errors like this
runtime error: Cannot modify null.x.
proc name: load (/mob/proc/load)
  source file: Login.dm,30

And I cannot figure the problem out...

proc name: load (/mob/proc/load)
  source file: Login.dm,30
  usr: null
  src: Pika1516 (/mob)
  call stack:
Pika1516 (/mob): load()
the load (16,2,1) (/turf/load): Click(the load (16,2,1) (/turf/load), "mapwindow.map", "icon-x=32;icon-y=12;left=1;scr...")
The mob may randomly not load at all despite the save being in the correct folder.
#1 Jun 21 2011, 12:10 am
Don't use usr in procs.
#2 Jun 21 2011, 5:32 am
You should use Write and Read procs for saving and loading, but you will have to overwrite them to be able to save the location.
mob/verb/Save()
    var/savefile/F= new("savespot/[usr.ckey].sav")//this will make new savefile if there is none with such name, but will "import" it in the game for the use if there is one
    usr.Write(F)//calls built-in Write proc, which saves all non-tmp vars
    usr<<"Saved!"//outputs the message
    
mob/verb/Load()
    if(fexists("savespot/[usr.ckey].sav"))//You don't want to load someone without savefile
        var/savefile/F= new("savespot/[usr.ckey].sav")//and this will only import the savefile for the use, it won't remove it
        usr.Read(F)//Calls Read proc, which will update the vars with info in the savefile
        usr<<"Loaded!"
    else
        usr<<"You have no savefile!"    
    
                
mob 
    //Write and Read don't automatically save the coordinates, so you will have to overwrie them            
    Write(F)//A write proc is for saving info into a file           
        F["x"]<< src.x//on saving, we just add new "path"(which is "x") and set it to our coordinate, then do it with other coordinates
        F["y"]<< src.y
        F["z"]<< src.z
        ..()//we also want to save other vars too, but we can easily do it by calling parent proc with ..() and save us some time
    Read(F)//A read proc reads the info from the savefile and edits the vars to it
        F["x"]>> src.x//this will edit the x var to the one we saved before, do this to the other coordinates too and you willbe moved where you saved
        F["y"]>> src.y
        F["z"]>> src.z
        ..()//we need to read other vars too
#3 Jun 21 2011, 5:52 am
In response to Martys1103 (#2)
You should not be calling Read() and Write() directly, it can have ill effects on a savefile. A good example of how to do this properly can be found at [link].