Description
Tests whether a variable is nil or undefined from its identifier, or whether the given expression evaluates to nil or Nothing.
Note
This command does not exist in Operation Flashpoint/Arma: Cold War Assault but can be emulated (see #Example 5).
Syntax
Syntax 1
isNil variableName
Parameters:
variableName: String - missionNamespace's or local variable's identifier (e.g "globalVariable", "_localVariable")
Returns: Boolean - true if variable is nil or undefined
Syntax 2
isNil code
Parameters:
code: Code - code to evaluate:- the code will be executed;
isNil { player setDamage 1 };will kill the player - the code will not be allowed to suspend while expression is evaluated, even if the parent scope allows it (see #Example 4).
- the code will be executed;
Returns: Boolean - true if code returns Nothing, false otherwise
Syntax 3
since arma3 2.18
namespace isNil variableName
Parameters:
Returns: Boolean - true if variable is nil or undefined
Examples
Example 1
if (isNil "TAG_globalVariable") then { TAG_globalVariable = 0 };
if (isNil "_localVariable") then { hint "_localVariable is nil" };
Example 2
isNil { player getVariable "someVar" };
Example 3
_myArray = [0, 1];
isNil { _myArray select 0 }; // returns false
isNil { _myArray select 1 }; // returns false
isNil { _myArray select 2 }; // returns true
isNil { _myArray select 3 }; // throws a script error. only length+1 select is allowed
Example 4
This trick forces executing something in Unscheduled Environment:
0 spawn {
systemChat str canSuspend; // chat shows true
isNil { hint str canSuspend }; // hint shows false
};
Example 5
Operation Flashpoint String comparison workaround
_nil = format ["%1", _undefinedVariable]
? (format ["%1", variableToTest] == _nil) : hint "variableToTest is nil"
_nil = format ["%1", _undefinedVariable];
if (format ["%1", variableToTest] == _nil) then { hint "variableToTest is nil" };