Saving Datums...

ID:159329
 
Mar 29 2009, 5:16 pm
I've been trying for hours to save my datums.


There was an article about datums, could someone help me with saving them.
Mar 29 2009, 8:37 pm
If you were to look up Write/Read in the DM reference, you'd notice that it is actually datum based... Meaning absolutely anything you could ever make in BYOND can be saved using those procs.

Or you can be all over-active and do it this way:
var/MYDATUM=NEW /MYDATUM
var/savefile/F=new("blahblah.sav")
F["DATUM!?"]<<MYDATUM
Mar 30 2009, 5:32 am
Read the DM Guide's savefile chapter and relevant entries in the DM Reference. Datums are saved just like any other object - which can also be saved similarly to any value at all anyway. I wonder what's so difficult to keep you for hours, since if I had to take a guess I'd say you've implemented at least saving of mobs before. This isn't any different.
Mar 30 2009, 8:39 am
In response to AJX
You forgot the Write(F) line ^-^
Mar 30 2009, 10:22 am
In response to Spunky_Girl
Actually, when you use the '<<' operator to save something you call the Write() proc, and when you use '>>' operator to read something you call the Read() proc.

So, no need to use it.
Mar 30 2009, 10:24 am
In response to Spunky_Girl
No, he didn't. It's a somewhat common misconception, but you don't actually realize what that proc does - it's for saving objects into a savefile, and it's an object proc, not a global (or a savefile, of course) proc. So that would really compile as src.Write(). His usage of << already saves the object and calls Write() internally; for more info refer to the Reference & Guide.
Mar 30 2009, 11:35 am
In response to Kaioken
If he wanted to save all the non-tmp variables of the datum, couldn't he just call MyDatum.Write(F)? In case he didn't want to use << for all the variables manually, I mean.
Mar 30 2009, 11:42 am
In response to Kaiochao
Yes... This is correct.
Mar 31 2009, 3:28 am
In response to Kaiochao
He could, but apparently you didn't read my post or something (?), since it already said using << on the object reference (like AJX did in his psuedocode) does do a complete object save by calling Write(), though the result is different from calling only Write() alone. Same with >> and Read(), so both methods shouldn't be mixed.
Mar 31 2009, 10:25 am
In response to Kaioken
By "mixed" do you mean you should never use the shift operators in Read/Write procs and vice-versa? or do you mean they should just never be used at the same time in a proc?

var/list/stuff = list()
proc/Save()
    var/savefile/s = new("file.sav")
    s["stuff"] << stuff
    Write(s)

//or...

mob/Write(savefile/s)
    s["stuff"] << stuff
    ..()
Mar 31 2009, 10:53 am
In response to Spunky_Girl
Spunky_Girl wrote:
By "mixed" do you mean you should never use the shift operators

When used with savefiles, they're not really shift operators of course, since they're not shifting anything. The DM Reference calls them "savefile operators".

in Read/Write procs and vice-versa? or do you mean they should just never be used at the same time in a proc?

The latter couldn't be accurately said since you could potentially have multiple dealings of saving/loading objects in a single proc, etc. You generally shouldn't mix them within the same saving/loading context - they have different uses and you shouldn't use both, doing which would only potentially cause harm and it's pointless anyway. It looks like you still don't completely understand the Write() and Read() procs, as your first example doesn't even involve objects and wouldn't compile either, so allow me to illustrate: 
var/savefile/F = new
F << MyObject
MyObject.Write(F)

If you do this, you've obviously just saved the object twice. No point there. You should only use one of the methods.
Additionally, since the 2 methods (using savefile operators or savefile procs) work a little differently you need to stick with one method, ie don't use >> to load what you've saved by calling Write(); use Read().
//Examples:
mob/proc
   //Bad
   Save()
      var/savefile/F = new(src.ckey)
      F << src
      src.Write(F)
      //mob was saved twice
   Load()
      var/savefile/F = new(src.ckey)
      F >> src
      src.Read(F)
      //was of course loaded twice    
//-----------------------
   //Also bad
   Save()
     var/savefile/F = new(src.ckey)
     F << src
   Load()
     var/savefile/F = new(src.ckey)
     src.Read(F) //mixing of different methods

Also, what you've done in the 2nd example, overriding Write(), is of course different. Overriding the savefile procs allows you to have control on how objects are saved/loaded, which is of course handy, and works irregardless of what saving method is used since the operators use and call Read()&Write() as well.
For more info or if you still have questions do consult the DM Guide & Reference. It's all documented there so reading them before asking further questions is recommended. The DM Guide has a whole chapters on savefiles and how to use them and the DM Reference's entries on the savefile procs and operators explain how those work. =)
Mar 31 2009, 12:16 pm
In response to Kaioken
Alright I get it now. Thanks. I know my first example wouldn't load because Write()/Read() are atom based procs ("datum" as said in the reference).
Mar 31 2009, 1:20 pm
In response to Spunky_Girl
I figured out the problem a few days ago, forgot to come back and let you know.