isNil: Difference between revisions

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m (Text replacement - "\[\[#Examples\|Example ([0-9])\]\]" to "{{HashLink|#Example $1}}")
(Fix description and examples)
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|gr1= Variables
|gr1= Variables


|descr= Tests whether the variable given by its name is [[nil]] or undefined, or whether the given expression evaluates to [[nil]] or [[Nothing]].
|descr= Tests whether a variable is [[nil]] or undefined from its [[Identifier|identifier]], or whether the given expression evaluates to [[nil]] or [[Nothing]].
{{Feature | Informative | {{GVI|ofp|1.00}} This command doesn't exist in {{ofp}} but can be emulated (see '''{{HashLink|#Example 5}}''').}}
{{Feature | arma0 | This command does not exist in {{ofp}}/{{arma0}} but can be emulated (see {{HashLink|#Example 5}}).}}


|s1= [[isNil]] variableName
|s1= [[isNil]] variableName


|p1= variableName: [[String]] - name of a [[missionNamespace]] variable (e.g "someVar") or a local variable (e.g "_someVar")
|p1= variableName: '''[[String]]''' - [[missionNamespace]]'s or local [[Variables|variable]]'s [[Identifier|identifier]] (e.g "globalVariable", "_localVariable")


|r1= [[Boolean]] - [[true]] if variable is [[nil]]
|r1= [[Boolean]] - [[true]] if variable is [[nil]]
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|p21= code: [[Code]] - code to evaluate:
|p21= code: [[Code]] - code to evaluate:
* the code '''will''' be executed; {{ic|[[isNil]] { [[player]] [[setDamage]] 1; };}} ''will'' kill the player
* the code '''will''' be executed; {{ic|[[isNil]] { [[player]] [[setDamage]] 1 };}} ''will'' kill the player
* the code will not be allowed [[canSuspend|to suspend]] while expression is evaluated, even if the parent scope allows it (see '''{{HashLink|#Example 4}}''').
* the code will not be allowed to [[canSuspend|suspend]] while expression is evaluated, even if the parent scope allows it (see {{HashLink|#Example 4}}).


|r2= [[Boolean]] - [[true]] if code returns something other than [[Nothing]]
|r2= [[Boolean]] - [[false]] if ''code'' returns [[Nothing]], [[true]] otherwise


|x1= <code>[[if]] ([[isNil]] "pokus") [[then]] { pokus = 0; };</code>
|x1= <code>[[if]] ([[isNil]] "TAG_globalVariable") [[then]] { TAG_globalVariable = 0 };
[[if]] ([[isNil]] "_localVariable") [[then]] { [[hint]] "_localVariable is nil" };</code>


|x2= <code>[[isNil]] { [[player]] [[getVariable]] "someVar" };</code>
|x2= <code>[[isNil]] { [[player]] [[getVariable]] "someVar" };</code>
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</code>
</code>


|x4= You can do this trick to force execute something in [[Scheduler|Unscheduled Environment]].<code>[[spawn]] {
|x4= This trick forces executing something in [[Scheduler|Unscheduled Environment]]:<code>0 [[spawn]] {
[[systemChat]] [[str]] [[canSuspend]]; {{cc|chat shows [[true]]}}
[[systemChat]] [[str]] [[canSuspend]]; {{cc|chat shows [[true]]}}
[[isNil]] {[[hint]] [[str]] [[canSuspend]]}; {{cc|hint shows [[false]]}}
[[isNil]] { [[hint]] [[str]] [[canSuspend]] }; {{cc|hint shows [[false]]}}
};</code>
};</code>


|x5= {{ofp}} workaround:<br>SQS syntax:
|x5= {{ofp}} [[String]] comparison workaround:
<code>_nil = [[format]] ["%1", _undefinedVariable]
<code>{{codecomment|; [[SQS Syntax]]}}
? ([[format]] ["%1", foo] == _nil) : foo = "value"</code>
_nil = [[format]] ["%1", _undefinedVariable]
SQF syntax:
? ([[format]] ["%1", variableToTest] == _nil) : [[hint]] "variableToTest is nil"</code>
<code>_nil = [[format]] ["%1", _undefinedVariable];
<code>{{cc|[[SQF Syntax]]}}
[[if]] ([[format]] ["%1", foo] == _nil) [[then]] { foo = "value"; };</code>
_nil = [[format]] ["%1", _undefinedVariable];
[[if]] ([[format]] ["%1", variableToTest] == _nil) [[then]] { [[hint]] "variableToTest is nil" };</code>


|seealso= [[nil]], [[Variables]], [[Scheduler]]
|seealso= [[nil]], [[Variables]], [[Scheduler]]
}}
}}

Revision as of 10:53, 26 August 2021

Logo A1 black.png1.00Logo A2.png1.00A2 OA Logo.png1.50tkoh logo small.png1.00Arma 3 logo black.png0.50
Hover & click on the images for description

Description

Description:
Tests whether a variable is nil or undefined from its identifier, or whether the given expression evaluates to nil or Nothing.
Operation Flashpoint
This command does not exist in Operation Flashpoint/Arma: Cold War Assault but can be emulated (see Example 5).
Groups:
Variables

Syntax

Syntax:
isNil variableName
Parameters:
variableName: String - missionNamespace's or local variable's identifier (e.g "globalVariable", "_localVariable")
Return Value:
Boolean - true if variable is nil

Alternative Syntax

Syntax:
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).
Return Value:
Boolean - false if code returns Nothing, true otherwise

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: ; SQS Syntax _nil = format ["%1", _undefinedVariable] ? (format ["%1", variableToTest] == _nil) : hint "variableToTest is nil" // SQF Syntax _nil = format ["%1", _undefinedVariable]; if (format ["%1", variableToTest] == _nil) then { hint "variableToTest is nil" };

Additional Information

See also:
nilVariablesScheduler

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
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