isNull: Difference between revisions

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{{Command|Comments=
{{RV|type=command
____________________________________________________________________________________________


| ofp |Game name=
|game1= ofp
|version1= 1.00


|1.00|Game version=
|game2= ofpe
|version2= 1.00


|arg= global |Multiplayer Arguments=
|game3= arma1
____________________________________________________________________________________________
|version3= 1.00


|   Checks whether the tested item is Null.<br>
|game4= arma2
Which null type the item has to be equal to depends on the type of game entity tested:<br>
|version4= 1.00
* [[Object]]s -> [[objNull]]
* [[Control]]s -> [[controlNull]]
* [[Display]]s -> [[displayNull]]
* [[Group]]s -> [[grpNull]]
* [[Location]]s -> [[locationNull]] (since ARMA 2)
* [[Task]]s -> [[taskNull]] (since ARMA 2)
* [[Script]]s -> [[scriptNull]] (since Arma 3 1.29.127075)
* [[Config]]s -> [[configNull]] (since Arma 3 1.53.133130)


Note: A test via <nowiki>==</nowiki> does not work, because, for example, [[objNull]] is not equal to anything, not even to itself. Use [[isEqualTo]]. |DESCRIPTION=
|game5= arma2oa
____________________________________________________________________________________________
|version5= 1.50


| '''isNull''' entity |SYNTAX=
|game6= tkoh
|version6= 1.00


|p1 = entity: [[Object]], [[Control]], [[Display]], [[Group]] (or [[Location]], [[Task]] since ARMA 2 (or [[Script]] since Arma 3 1.29.127075)) |PARAMETER1=
|game7= arma3
|version7= 0.50


| [[Boolean]] |RETURNVALUE=
|arg= global
____________________________________________________________________________________________


|x1 = <code>[[if]] ([[isNull]] obj) [[then]] {[[hint]] "doesn't exist";};</code>
|gr1= Variables


| [[controlNull]], [[displayNull]], [[grpNull]], [[locationNull]], [[objNull]], [[taskNull]], [[teamMemberNull]], [[scriptNull]], [[configNull]], [[typeName]]|SEEALSO=
|descr= Checks whether the tested item is null.<br>
Which null type the item has to be equal to depends on the type of game entity tested:


}}
{{{!}} class="wikitable" style="text-align: center"
! [[:Category:Data Types|Type]]
{{!}} [[Object]]
{{!}} [[Group]]
{{!}} [[Control]]
{{!}} [[Display]]
{{!}} [[Location]]
{{!}} [[Task]]
{{!}} [[Script Handle|Script]]
{{!}} [[Config]]
{{!}} [[Diary Record]]
{{!}} [[Team Member]]
{{!}}-
! Null value
{{!}} [[objNull]]
{{!}} [[grpNull]]
{{!}} [[controlNull]]
{{!}} [[displayNull]]
{{!}} [[locationNull]]
{{!}} [[taskNull]]
{{!}} [[scriptNull]]
{{!}} [[configNull]]
{{!}} [[diaryRecordNull]]
{{!}} [[teamMemberNull]]
{{!}}- style="font-size: .85em"
! Since
{{!}} colspan="2" {{!}} {{GVI|ofp|1.00}}
{{!}} colspan="2" {{!}} {{GVI|arma1|1.00}}
{{!}} colspan="2" {{!}} {{GVI|arma2|1.00}}
{{!}} {{GVI|arma3|1.30}}
{{!}} {{GVI|arma3|1.54}}
{{!}} {{GVI|arma3|2.00}}
{{!}} {{GVI|arma3|2.10}}
{{!}}}
 
{{Feature|important|2= A test ''via'' [[a == b|==]] does '''not''' work because a null value is not equal to anything, not even itself ([[configNull]] being the exception).
See also [[isEqualTo]].}}
 
|s1= [[isNull]] entity
 
|p1= entity: [[Object]], [[Control]], [[Display]], [[Group]], [[Location]], [[Task]], [[Script Handle]], [[Config]] or [[Diary Record]]
 
|r1= [[Boolean]]
 
|x1= <sqf>
if (isNil "obj") exitWith { hint "obj variable is undefined" };


<h3 style="display:none">Notes</h3>
if (isNull obj) then
<dl class="command_description">
{
<!-- Note Section BEGIN -->
hint "obj variable is defined but is null";
<!-- Note Section END -->
}
</dl>
else
{
hint "obj variable is defined and is not null";
};
</sqf>


<h3 style="display:none">Bottom Section</h3>
|x2= [[Diary Record]] support before {{GVI|arma3|2.00}}:
[[Category:Scripting Commands|ISNULLOBJ]]
<sqf>
[[Category:Scripting Commands OFP 1.99|{{uc:{{PAGENAME}}}}]]
private _nullRecord = objNull createDiaryRecord []; // wrong parameters = failure to create a record = null value
[[Category:Scripting Commands OFP 1.96|ISNULLOBJ]]
private _createdRecord = player createDiaryRecord ["Diary", ["title", "description"]];
[[Category:Scripting Commands OFP 1.46|ISNULLOBJ]]
if (_createdRecord isEqualTo _nullRecord) then { hint "Failed" };
[[Category:Scripting Commands ArmA|ISNULLOBJ]]
</sqf>
[[Category:Command_Group:_Object_Information|{{uc:{{PAGENAME}}}}]]
[[Category:Command_Group:_Variables|{{uc:{{PAGENAME}}}}]]
[[Category:Scripting Commands Arma 2|{{uc:{{PAGENAME}}}}]]
[[Category:Scripting Commands Arma 3|{{uc:{{PAGENAME}}}}]]
[[Category:Scripting_Commands_Take_On_Helicopters|{{uc:{{PAGENAME}}}}]]


<!-- CONTINUE Notes -->
[[Team Member]] support before {{GVI|arma3|2.10}}:
<dl class="command_description">
<sqf>private _isNull = _teamMember isEqualTo teamMemberNull;</sqf>
<dd class="notedate">Posted on December 9, 2015 - 11:29 (UTC)</dd>
<dt class="note">[[User:Commy2|Commy2]]</dt>
<dd class="note">
isNull does not work with the TEAM_MEMBER type.
Use this instead:
<code>_tmember isEqualTo teamMemberNull</code>
</dd>
</dl>
<!-- DISCONTINUE Notes -->


<!-- CONTINUE Notes -->
|seealso= [[controlNull]] [[displayNull]] [[grpNull]] [[locationNull]] [[objNull]] [[taskNull]] [[teamMemberNull]] [[scriptNull]] [[configNull]] [[typeName]]
<dl class="command_description">
}}
<dd class="notedate">Posted on December 9, 2015 - 11:38 (UTC)</dd>
<dt class="note">[[User:Commy2|Commy2]]</dt>
<dd class="note">
The note in the description does not apply to the CONFIG type, probably due to backwards compatibility.<br>
<code>configNull == configNull
-> true
</code>
</dd>
</dl>
<!-- DISCONTINUE Notes -->

Latest revision as of 21:32, 19 September 2024

Logo A0.png1.00ofpe logo.png1.00Logo A1 black.png1.00Logo A2.png1.00A2 OA Logo.png1.50tkoh logo small.png1.00Arma 3 logo black.png0.50
GAGlobal
Hover & click on the images for description

Description

Description:
Checks whether the tested item is null.
Which null type the item has to be equal to depends on the type of game entity tested:
Type Object Group Control Display Location Task Script Config Diary Record Team Member
Null value objNull grpNull controlNull displayNull locationNull taskNull scriptNull configNull diaryRecordNull teamMemberNull
Since Logo A0.png1.00 Logo A1 black.png1.00 Logo A2.png1.00 Arma 3 logo black.png1.30 Arma 3 logo black.png1.54 Arma 3 logo black.png2.00 Arma 3 logo black.png2.10
⚠
A test via == does not work because a null value is not equal to anything, not even itself (configNull being the exception). See also isEqualTo.
Groups:
Variables

Syntax

Syntax:
isNull entity
Parameters:
entity: Object, Control, Display, Group, Location, Task, Script Handle, Config or Diary Record
Return Value:
Boolean

Examples

Example 1:
if (isNil "obj") exitWith { hint "obj variable is undefined" }; if (isNull obj) then { hint "obj variable is defined but is null"; } else { hint "obj variable is defined and is not null"; };
Example 2:
Diary Record support before Arma 3 logo black.png2.00:
private _nullRecord = objNull createDiaryRecord []; // wrong parameters = failure to create a record = null value private _createdRecord = player createDiaryRecord ["Diary", ["title", "description"]]; if (_createdRecord isEqualTo _nullRecord) then { hint "Failed" };
Team Member support before Arma 3 logo black.png2.10:
private _isNull = _teamMember isEqualTo teamMemberNull;

Additional Information

See also:
controlNull displayNull grpNull locationNull objNull taskNull teamMemberNull scriptNull configNull typeName

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
Retrieved from "https://community.bistudio.com/wiki?title=isNull&oldid=369554"