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-wrong parameter ("Arma") defined!-1.00
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Adds given code to the scheduler. Exactly when the code will be executed is unknown, it depends on how busy is the engine and how filled up is the scheduler. Therefore spawn does not wait for the supplied code to finish, instead, spawn returns a Script handle to the scheduler task. scriptDone command can be used to check the code completion. Additional arguments are passed to the code in local variable _this. Since Arma 3 v1.55 the script handle also exists inside the code in _thisScript variable.


arguments spawn code
arguments: Any Value - arguments passed to the script, which later available in _this variable inside the script.
code: Code
Return Value:
Script Handle - can be used to determine (via scriptDone (also via isNull in Arma 3)) when the spawned script has finished. In Arma 3, the handle is also available inside the spawned script in _thisScript variable.


Example 1:
_handle = [] spawn {player globalChat "Hello world!"};
Example 2:
There is no guarantee that spawned scripts will be executed in the same order they spawned: for "_i" from 0 to 100 do { _null = _i spawn { diag_log _this; }; }; // Result: 51,1,2...49,50,0,52,53...100

Additional Information

See also:


Report bugs on the Feedback Tracker and/or discuss them on the Arma Discord or on the Forums.
Only post proven facts here! Add Note


Posted on 5 March, 2009
spawn cannot call other local functions on the same scope as itself.
It can, however, call other global functions: _addOne = {TST=TST+1}; TST_addOne = {TST=TST+1}; _add = { TST=TST+1; player sideChat format ["added: %1",TST]; [] call _addOne; player sideChat format ["called local: %1",TST]; [] call TST_addOne; player sideChat format ["called global: %1",TST]; }; TST=0; [] call _add; [] spawn _add; The call of _addOne from the spawned function does not do anything.

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Posted on October 21, 2014 - 23:33 (UTC)
spawn requires a script handle when used in the 2D editor. (A3)
In scripts and in the debug console, it is not required, but very useful for keeping track of running scripts. Having a script handle also makes it easy to terminate scripts at any time.

Since spawn creates a new scheduled environment, having an excess of open threads can make the scheduler queue extremely long, significantly increasing the execution time of each thread. (it takes an extremely large amount of threads, though)
Posted on August 25, 2015 - 13:39 (UTC)
If you want to call a local function which has NOT been created inside a spawned function, then do this: _fncOne = { systemChat"This is _fncOne" }; _fncTwo = { call (_this select 0) }; [_fncOne] spawn _fncTwo;

An argument is always required to spawn a function.
However, your function get's executed the fastest if you use nil as argument e. g.
myFnc = {systemChat "Hello"};
nil spawn myFnc;

Tested in Arma 3 1.62 [Tanoa Sneak Preview] with many Data_Types (and magic types) using BIS_fnc_codePerformance.

Using [] (Array),
['[] spawn myFnc',nil,1000] call BIS_fnc_codePerformance; //Results: 0.006 ms 0.005 ms 0.006 ms 0.005 ms 0.006 ms 0.006 ms 0.006 ms

Type Number
['0 spawn myFnc',nil,1000] call BIS_fnc_codePerformance; //Results: 0.005 ms 0.004 ms 0.005 ms 0.006 ms 0.006 ms 0.005 ms 0.005 ms

and using nil (Nothing)
['nil spawn myFnc',nil,1000] call BIS_fnc_codePerformance; //Results: 0.004 ms 0.003 ms 0.002 ms 0.002 ms 0.002 ms 0.002 ms 0.003 ms