Local variable overwritten by function

[Clayman 20]

I've ran into a strange problem with a script I'm working on. Not sure if it should be this way or if something is "glitched". Maybe someone can enlighten me.

So, basicly I have a script that selects a random set of vehicle and unit classnames and stores these in three local variables. Then these local variables are passed to a function that creates the vehicle and the units, moves the units into the vehicle and returns the group.

Simplified version of the script (initPatrol.sqf):

_units = ["TK_Soldier_SL_EP1", "TK_Soldier_EP1", "TK_Soldier_GL_EP1", "TK_Soldier_AR_EP1"];
_crew = ["TK_Soldier_Crew_EP1", "TK_Soldier_Crew_EP1"];
_vehicle = "M113_TK_EP1";

_grp = [_units, _crew, _vehicle] call compile preprocessFile "fn_create.sqf";

Hint format ["_units: %1\n\n_crew: %2\n\n_vehicle: %3\n\n_grp: %4", _units, _crew, _vehicle, _grp];

_units is the classnames of the units in cargo

_crew is the classnames of the vehicle crew

_vehicle is classname of the vehicle

Function to create the units (fn_create.sqf):

_u = _this select 0;
_c = _this select 1;
_v = _this select 2;
_p = "pos1";

_grp = [[0,0,0], EAST, _u] call BIS_fnc_spawnGroup;
_vehicle = _v createVehicle markerPos _p;
_crew = [];

_tmp = [[0,0,0], EAST, _c] call BIS_fnc_spawnGroup;
_crew = units _tmp;

_d = _crew select 0;
_d assignAsDriver _vehicle;
_d moveInDriver _vehicle;

_g = _crew select 1;
_g assignAsGunner _vehicle;
_g moveInGunner _vehicle;

If (count _crew == 3) Then
{
_o = _crew select 2;
_o assignAsCommander _vehicle;
_o moveInCommander _vehicle;
};

{
_x assignAsCargo _vehicle;
_x moveInCargo _vehicle;
} forEach units _grp;

_crew join _grp;
deleteGroup _tmp;

_grp

The function uses the same local variables _crew and _vehicle. But as these are local, it shouldn't conflict with the variables in the first script (initPatrol.sqf). Therefore the Hint at the end should return all the classnames for the variables _units, _crew and _vehicle. But this is only true for _units, while _crew and _vehicle return the actual units (e.g. O 1-1-B:1 etc.) as the variables in fn_create do.

And this is pretty much the part I don't understand. Can someone explain to me what's going wrong - either in the script or in my head. :confused:

[neokika 62]

Hey,

Try the private command.

_neo_

[sbsmac 0]

I'm afraid the problem is in your head :) If you don't declare variables 'private' they are not restricted in scope at all so when _crew is seen in fnc_create.sqf it is assumed to be the same "_crew" that was declared in the outer scope of init_patrol.sqf.

There is nothing 'magic' about putting variables in different files.

//File outer.sqf
_a =5 ;
call compile preprocessfile "inner.sqf";
hint format ["a is %1",_a] ;

//File inner.sqf
_a=100;

is, to all intents and purposes identical to

_a =5;
call { _a=100;} ;
hint format ["a is %1",_a] ;

and in both cases the hint will show 100 unless you use 'private' in the inner block.

BTW, squint is extremely good at picking up scope issues and even has a feature where you can right-click on a variable and ask it to show you the variable's scope - quite useful for helping to understand these kinds of issues. In your example above, squint would have warned you that the variables in fn_create.sqf might corrupt those in an outer scope (which is exactly what is happening).

[Clayman 20]

Most impressive, that did the trick. Thanks neokika.

It even mentions exact this situation on the wiki page. lol.

And thanks for the explaination sbsmac.