isNull: Difference between revisions

Latest revision as of 21:32, 19 September 2024

1.00

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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	1.00		1.00		1.00		1.30	1.54	2.00	2.10

⚠

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 2.00:
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 2.10:
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

@@ Line 1: / Line 1: @@
-{{Command|= Comments
+{{RV|type=command
-____________________________________________________________________________________________
-| ofp |= Game name
+|game1= ofp
+|version1= 1.00
-|1.00|= Game version
+|game2= ofpe
+|version2= 1.00
-|arg= global |= Arguments in MP
+|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 object 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)
-Note: A test via <nowiki>==</nowiki> does not work, because, for example, [[objNull]] is not equal to anything, not even to itself. |= Description
+|game5= arma2oa
-____________________________________________________________________________________________
+|version5= 1.50
-| '''isNull''' obj |= Syntax
+|game6= tkoh
+|version6= 1.00
-|p1 = obj: [[Object]], [[Control]], [[Display]], [[Group]] (or [[Location]], [[Task]] since ARMA 2) |= Parameter 1
+|game7= arma3
+|version7= 0.50
-| [[Boolean]] |= Return value
+|arg= global
-____________________________________________________________________________________________
-|x1 = <code>[[if]] ([[isNull]] obj) [[then]] {[[hint]] "doesn't exist";};</code>
+|gr1= Variables
-| [[controlNull]], [[displayNull]], [[grpNull]], [[locationNull]], [[objNull]], [[taskNull]], [[teamMemberNull]] |= See also
+|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}}
+{{!}}}
-<h3 style="display:none">Notes</h3>
+{{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).
-<dl class="command_description">
+See also [[isEqualTo]].}}
-<!-- Note Section BEGIN -->
-<!-- Note Section END -->
+|s1= [[isNull]] entity
-</dl>
-<h3 style="display:none">Bottom Section</h3>
+|p1= entity: [[Object]], [[Control]], [[Display]], [[Group]], [[Location]], [[Task]], [[Script Handle]], [[Config]] or [[Diary Record]]
-[[Category:Scripting Commands|ISNULLOBJ]]
-[[Category:Scripting Commands OFP 1.96|ISNULLOBJ]]
-[[Category:Scripting Commands OFP 1.46|ISNULLOBJ]]
-[[Category:Scripting Commands ArmA|ISNULLOBJ]]
-[[Category:Command_Group:_Object_Information|{{uc:{{PAGENAME}}}}]]
-[[Category:Command_Group:_Variables|{{uc:{{PAGENAME}}}}]]
-[[Category:Scripting Commands ArmA2|{{uc:{{PAGENAME}}}}]]
-[[Category:Scripting Commands Arma 3|{{uc:{{PAGENAME}}}}]]
-[[Category:Scripting_Commands_Take_On_Helicopters|{{uc:{{PAGENAME}}}}]]
-{{subst:Add new note/construct|
+|r1= [[Boolean]]
-<!--
-* Replace from here (including the arrow just above)
-* Please add your note here, replacing these comments
+|x1= <sqf>
-* Please '''PREVIEW YOUR ADDITION BEFORE SAVING'''
+if (isNil "obj") exitWith { hint "obj variable is undefined" };
-* Thank you
-* Equal symbols "=" should be added as "{{subst:=}}" (excluding quotes)
+if (isNull obj) then
-* Pipes "|" should be added as "{{subst:!}}" (excluding quotes)
+{
-* New lines should be forced by the use of "<br>" tags
+	hint "obj variable is defined but is null";
-* Examples should be placed between tags <code>_like {{subst:=}} [[_this]];</code>
+}
+else
+{
+	hint "obj variable is defined and is not null";
+};
+</sqf>
-* Replace to here (including the arrow just below)
+|x2= [[Diary Record]] support before {{GVI|arma3|2.00}}:
-locationNull could be confusing when testing destinationTask :
+<sqf>
-if a task is created, taskDestination returns an array working as position : _mytask_distance = (taskDestination (currentTask player)) distance player;
+private _nullRecord = objNull createDiaryRecord []; // wrong parameters = failure to create a record = null value
-When task completed Hint format ["%1", taskDestination (currentTask player)] returns <null> while !isnull taskdestination.. leads to an error.
+private _createdRecord = player createDiaryRecord ["Diary", ["title", "description"]];
-correct test : _destination_task = taskDestination (currentTask player); if (!isNil "_destination_tsk") then {...
+if (_createdRecord isEqualTo _nullRecord) then { hint "Failed" };
+</sqf>
+[[Team Member]] support before {{GVI|arma3|2.10}}:
+<sqf>private _isNull = _teamMember isEqualTo teamMemberNull;</sqf>
+|seealso= [[controlNull]] [[displayNull]] [[grpNull]] [[locationNull]] [[objNull]] [[taskNull]] [[teamMemberNull]] [[scriptNull]] [[configNull]] [[typeName]]
 }}