Group Bool GetVariable A2OA Trap Reference

Group Bool getVariable — A2-OA Engine Trap Reference (WFBE_CO_FNC_GroupGetBool)

Source-verified 2026-06-23 against master f8a76de3. Paths relative to Missions/[55-2hc]warfarev2_073v48co.chernarus/ unless noted. Arma 2 OA 1.64.

WFBE_CO_FNC_GroupGetBool is the platform-layer safe accessor for reading a boolean (or any defaulted) variable off a group receiver. It exists to work around a specific Arma 2 OA 1.64 engine quirk where the convenient 2-arg getVariable [name, default] form does not behave as documented on groups. This page documents the trap, the fix, where it is registered, and every call site that depends on it.

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1. The engine trap (what breaks, why groups specifically)

The function header states the quirk and its class label ("G1") directly. Header comment Common/Functions/Common_GroupGetBool.sqf:1-9 (the block's Params/Returns lines :11-12 are shown separately in §2; the comment closes at :13):

/*
	WFBE_CO_FNC_GroupGetBool — safe boolean getVariable for GROUP receivers.

	A2 OA 1.64 trap (the "G1" class): the 2-arg `group getVariable [name, default]`
	form returns nil (NOT the default) when the var is UNSET on a GROUP. Reading a
	bool that way and using it (`nil || {..}`, `if (nil)`, `nil != x`, ...) throws
	"Type Nothing". Side logics / objects / namespaces do NOT have this quirk — only
	groups — so route GROUP bool reads through this helper. It restores the intended
	default-on-missing semantics using the safe 1-arg form + isNil.
*/

The failure mode: code reads a flag that has never been setVariable'd on a particular group (the common case — most groups are never marked HC, founded, persistent, etc.), expects the supplied default, but instead gets nil. The moment that nil is consumed by a boolean operator (!x, x || {..}, if (x)), the engine throws Type Nothing and the surrounding script aborts. Because the heaviest readers are the per-frame AI Commander loop and the base-GC FSM, an unguarded read here would intermittently break commander tasking and group garbage collection — exactly the symptom the "B66" fix annotations across the call sites refer to.

The quirk is receiver-specific: objects, side logics, and namespaces all honour the 2-arg default form, so only group reads must be routed through this helper (Common/Functions/Common_GroupGetBool.sqf:7-8).

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2. The safe implementation

The body takes a 3-element array, reads via the safe 1-arg form, and substitutes the default itself when the result is nil. Full body Common/Functions/Common_GroupGetBool.sqf:14-19:

private ["_grp","_name","_default","_v"];
_grp     = _this select 0;
_name    = _this select 1;
_default = _this select 2;
_v = _grp getVariable _name;
if (isNil "_v") then {_default} else {_v}

Contract (Common/Functions/Common_GroupGetBool.sqf:11-12):

• Params: [ group, varName (string), default ]
• Returns: the stored value, or default when the var is unset/nil.

Key detail: the read uses the 1-arg _grp getVariable _name (Common/Functions/Common_GroupGetBool.sqf:18), which is the form the engine does NOT corrupt; the isNil "_v" guard (:19) then performs the default substitution in script rather than trusting the engine. The default need not be a boolean — element 0 of an array default works the same way (see the wfbe_aicom_order reader in §4).

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3. Registration

Compiled into missionNamespace during common init alongside the other WFBE_CO_FNC_* helpers. Common/Init/Init_Common.sqf:114:

WFBE_CO_FNC_GroupGetBool = Compile preprocessFileLineNumbers "Common\Functions\Common_GroupGetBool.sqf"; //--- G1: safe bool getVariable for GROUP receivers (A2 OA unset->nil trap)

It is registered just after WFBE_CO_FNC_CreateGroup (Common/Init/Init_Common.sqf:113) and before the unit/vehicle factory helpers (Common/Init/Init_Common.sqf:115-118), so it is available to every server-side AI and FSM consumer.

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4. Call-site taxonomy

Grepping the whole worktree, Call WFBE_CO_FNC_GroupGetBool resolves to 21 call occurrences on 15 lines across 4 files — several lines invoke it 2–3× inside one || chain (e.g. server_groupsGC.sqf:209 ORs three flag reads, and AI_Commander.sqf:305/:354 each OR two):

File	Calls	On lines
Server/FSM/server_groupsGC.sqf	10	:75(×2), :117, :118(×2), :122, :154, :209(×3)
Server/AI/Commander/AI_Commander.sqf	6	:314(×2), :370(×2), :462, :463
Server/AI/Commander/AI_Commander_Produce.sqf	4	:69, :138, :196, :331
Server/AI/Commander/AI_Commander_Execute.sqf	1	:55

(AI_Commander_Produce.sqf:66 and AI_Commander_MHQReloc.sqf:191 only mention the helper in comments and are not calls.) The call sites carry //--- B66 / //--- G1 annotations marking them as the A2-OA-safe group-bool conversion (e.g. AI_Commander_Produce.sqf:196, :331).

The group-state flags read through it:

Flag	Default	Meaning	Representative read	Setter
wfbe_aicom_hc	false	Group is an HC (headless-client) commanded team; brain must not Produce/waypoint it directly.	Server/AI/Commander/AI_Commander_Produce.sqf:69	Common/Functions/Common_RunCommanderTeam.sqf:66 (broadcast)
wfbe_aicom_founded	false	Server-local team re-adopted/founded by the base-GC; eligible for refill at a factory.	Server/AI/Commander/AI_Commander.sqf:447	Server/AI/Commander/AI_Commander_Teams.sqf:602; Server/FSM/server_groupsGC.sqf:158
wfbe_aicom_refit	false	Team is marked to top-up at base once home (B61).	Server/AI/Commander/AI_Commander_Produce.sqf:196	Server/AI/Commander/AI_Commander_Produce.sqf:176 (set true), :332 (clear)
wfbe_aicom_order	[-1]	Current order tuple [seq, mode, pos, ...]; read defaulted then select 0 for the sequence number.	Server/FSM/server_groupsGC.sqf:154	Server/AI/Commander/AI_Commander_Execute.sqf:61; Server/AI/Commander/AI_Commander_AssignTowns.sqf:151; Server/AI/Commander/AI_Commander_Strategy.sqf:397
wfbe_persistent	false	Group is a persistent garrison/defense team; base-GC must not reap it.	Server/FSM/server_groupsGC.sqf:117	Server/AI/Commander/AI_Commander_Teams.sqf:605; Server/Init/Init_Server.sqf:717; many others
WFBE_SidePatrol	false	Group is a side-patrol; must not be re-adopted/re-tasked by the base-GC.	Server/FSM/server_groupsGC.sqf:122	Common/Functions/Common_RunSidePatrol.sqf:63 (broadcast)

Notes:

• The wfbe_aicom_order case proves the helper is not boolean-only: it is read with a non-bool default [-1] and immediately select 0'd for the sequence (Server/FSM/server_groupsGC.sqf:154). Without the helper, an unset order on a group would return nil, and (nil) select 0 would throw.
• wfbe_aicom_hc and WFBE_SidePatrol setters broadcast (setVariable [..., true]) so the server can read them on groups it does not own — Common/Functions/Common_RunCommanderTeam.sqf:66 and Common/Functions/Common_RunSidePatrol.sqf:63. The server-side comment at Server/FSM/server_groupsGC.sqf:119-121 documents this dependency.
• Every flag above has at least one setter; no read-without-setter (dead flag) was found among the call args.

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5. When to use / guidance

• Reading a boolean (or defaulted) variable off a GROUP → always route through WFBE_CO_FNC_GroupGetBool. The 2-arg group getVariable [name, default] form is unreliable for unset vars on a group in A2 OA 1.64 (Common/Functions/Common_GroupGetBool.sqf:4-9).
• Reading off an OBJECT, SIDE LOGIC, or NAMESPACE → the plain 2-arg obj getVariable [name, default] is fine — those receivers honour the default and do not exhibit the trap (Common/Functions/Common_GroupGetBool.sqf:7-8). Do not wrap object reads in this helper; it would just add overhead.
• If you must read a group var inline without the helper, use the safe 1-arg form plus an isNil guard — i.e. exactly what the helper does (Common/Functions/Common_GroupGetBool.sqf:18-19) — never the 2-arg default form on a group.
• When adding a new group-state flag, broadcast the setter (setVariable [name, value, true]) if the server reads it on groups owned by an HC, matching the wfbe_aicom_hc / WFBE_SidePatrol pattern.

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See also

• Namespace Profile And Diagnostic Utility Reference — sibling platform-layer accessor/diagnostic utility.
• AI Commander Execution Loop Reference — the heaviest consumer cluster; wfbe_aicom_hc, wfbe_aicom_founded, wfbe_aicom_refit and the wfbe_aicom_order tuple are all routed through the helper across its produce/tasking files (e.g. AI_Commander_Execute.sqf:55 reads wfbe_aicom_hc).
• Networking And Public Variables — the broadcast (setVariable [..., true]) semantics that let the server read HC-owned group flags.