UBTDecorator

class AIModule Since 4.0

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

#include "BehaviorTree/BTDecorator.h"

Description

The base class for Behavior Tree decorator nodes. Decorators sit on branches or tasks and act as conditional gates — they can allow or block execution and abort active branches when their condition changes.

Caveats & Gotchas

• Override CalculateRawConditionValue() to implement the condition. Do not override WrappedCanExecute() directly.
• Abort mode (Self, LowerPriority, Both) determines which branches are aborted when the condition changes at runtime. Wrong abort mode is the most common decorator bug.
• Like tasks, decorators are shared across all trees using the same asset unless instanced. Do not store mutable state on the object.

Example

Custom decorator checking a gameplay condition C++

bool UBTDecorator_HasAmmo::CalculateRawConditionValue(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory) const
{
    AMyAIController* Controller = Cast<AMyAIController>(OwnerComp.GetAIOwner());
    return Controller && Controller->GetAmmoCount() > 0;
}

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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