isNil

-wrong parameter ("Arma") defined!-1.00

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Description

Description:

Tests whether the variable defined by the String argument is undefined, or whether an expression result passed as Code is undefined.
The command returns true if the variable or the expression result is undefined (i.e. the expression result is Void), and false in all other cases.

Groups:

Uncategorised

Syntax

Syntax:

isnil variable

Parameters:

variable: String or Code

Return Value:

Boolean

Examples

Example 1:

if (isNil "_pokus") then { _pokus = 0; };

Additional Information

See also:

nilVariables

Notes

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

Notes

ColonelSandersLite

I recently had a strange experience with this command. I forgot to wrap the name of the variable with quotes, and it returned the opposite of the true null status of the variable. Just something to watch out for.

General Barron

^ If you don't wrap the name of the variable in quotes, then it will instead read the value of the variable itself. If that variable is a string or code, then the command will use that string or code held by the variable. Example:

_myvar = "_hisvar";
isnil _myvar;
//will return true if _hisvar is null
_myvar = {tank1};
sleep (random 50);
isnil _myvar;
//will return if tank1 is nil, at the time the isnil command is checked (not at the time _myvar is established)

--General Barron 10:37, 30 December 2009 (CET)

Igneous01

isNil is also able to check if an expression is undefined. As such, an alternative way to check variables would be:

isNil {variable}

you can use this method to also check if variables defined using setVariable exist as well:

isNil {player getVariable "Something"}

As well as testing if a function returns a value

func_ChangeVehicleName = 
{
   _this setVehicleVarName "newName";
};

if (isNil {player call func_ChangeVehicleName})    // returns true, because this function does not return anything

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Posted on September 25, 2014 - 09:48 (UTC)

Kenoxite

While isNil isn't available in OFP/CWA you can easily emulate it with something like this:

_nil = format["%1",_nilstring];
?(format["%1",foo]==_nil): foo = "Hello World!"

Posted on October 25, 2014 - 01:51 (UTC)

DreadedEntity

You can also use isNil to check if an array element exists. _array = [0,1,2,3]; if (isNil {_array select 4}) then {hint "Element does not exist";};

Posted on November 1, 2014 - 07:21 (UTC)

DreadedEntity

I forgot to mention in my last note, using the same method you can also check whether a variable has been defined using setVariable. if (isNil {missionNamespace getVariable "MY_VARIABLE"}) then //variable is nil {missionNamespace setVariable ["MY_VARIABLE", 999];}; //variable becomes 999 if (isNil {missionNamespace getVariable "MY_VARIABLE"}) then //variable is 999 {hint "MY_VARIABLE is nil!";} //skipped else {hint str (missionNamespace getVariable "MY_VARIABLE");}; //hint "999"