UBTService

class AIModule Since 4.0

Inherits: UObjectBase › UObjectBaseUtility › UObject › UBTNode › UBTAuxiliaryNode › UBTService

#include "BehaviorTree/BTService.h"

Description

The base class for Behavior Tree service nodes. Services run periodically in the background while their branch is active, typically updating blackboard values or performing lightweight checks.

Caveats & Gotchas

• Override TickNode() for periodic updates. The interval is controlled by Interval and RandomDeviation properties on the node.
• Services do not return results and cannot affect execution flow directly — use the Blackboard to communicate state to decorators and tasks.
• OnBecomeRelevant() and OnCeaseRelevant() are called when the service's branch becomes active or inactive — use these to start/stop ongoing work.

Example

Periodically update a target distance on the blackboard C++

void UBTService_UpdateTargetDist::TickNode(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory, float DeltaSeconds)
{
    AAIController* Controller = OwnerComp.GetAIOwner();
    AActor* Target = Cast<AActor>(OwnerComp.GetBlackboardComponent()->GetValueAsObject(FName("TargetActor")));
    if (Controller && Target)
    {
        float Dist = FVector::Dist(Controller->GetPawn()->GetActorLocation(), Target->GetActorLocation());
        OwnerComp.GetBlackboardComponent()->SetValueAsFloat(FName("TargetDistance"), Dist);
    }
}

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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