ShatalovBehavior

Developed with Unreal Engine 4.27

This is a super very basic task system that was used in the Hello Neighbor game from Prototype to Release. Originally developed by Anton Shatalov. The system is created on the UGameplayTask class, instead of UObject as in Hello Neighbor (due to the absence of UGameplayTask in UE4.8).

Project

The project includes a founder class (as AActor) and UBehavior itself.

UBehavior has the following main functions:

• RunBehavior - Running a new task
• FinishBehavior - Finishes the task
• SetIsInterrupted - Prevents all tasks from finishing before the task (including the current one) in which IsInterrupted was set
• Ready - Starts the task if it's not started yet.
• BehStart (Activate)
• BehTick (TickTask)
• RunBehMove (Only for AI) - Runs AI_MoveTo Task.
  

And pure functions:

• GetParentBehavior - Get reference to parent Behavior.
• GetChildBehavior - Get reference to child Behavior.
• GetBehaviorOwner - Returns the first Behavior (for example, if state is "BehMain -> BehAction -> BehAnim", the function will return a reference to BehMain).
• GetLastBehavior - Returns the last Behavior (for example, if state is "BehMain -> BehAction -> BehAnim", the function will return a reference to BehAnim).
• GetBehaviorInQueue - Get the next Behavior after finishing current.
• GetParallelBehaviors - Get current parallel Behaviors.

UBehavior also includes a prioritization system, where lower priority tasks are queued and high priority tasks overwrite other tasks.

Some of my ideas may not coincide with Anton Shatalov's ideas, for example, I didn't find an explanation for IsInterrupted in Hello Neighbor, so I rethought this variable for my project.

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Documentation (WIP)

Content:

• Delays
• Binding/Unbinding delegates
• FinishBehavior with Result
• Behavior Owner (Actor)
• Base tasks
• All _Implementation events

Delays

For safe use of GetWorldTimerManager()->SetTimer() - use special macro BehDelay();

Like this:

FTimerHandle TimerHandle; // If possible, move this declaration to the class header.

BehDelay(TimerHandle, 5.f, {
    <Code>
});

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Binding/Unbinding delegates

After you bind delegates with say:

GetAIController()->ReceiveMoveCompleted.AddDynamic(this, &UBehMove::OnMoveFinished);

MANDATORY, override the OnBehaviorFinished_Implementation event.

And unbind from delegates like this:

GetAIController()->ReceiveMoveCompleted.RemoveDynamic(this, &UBehMove::OnMoveFinished);

Otherwise, this event will be called again later (even after the task is completed, or the level is changed).

FinishBehavior with Result

You can finish tasks with Result state and FailedCode to help you track their execution.

For example:

void UBehCustomChild::SomeEvent()
{
    FinishBehavior(BR_Failed, "CantMove");
}

void UBehCustomParent::OnChildBehaviorFinished_Implementation(TSubclassOf<UBehavior> Behavior, EBehaviorResult Result, const FString& FailedCode)
{
    if (Result == BR_Failed && FailedCode == "CantMove")
    {
        UE_LOG(LogTemp, Error, TEXT("Hello, World!"));
    }
}

All states:

• BR_Success - Task executed successfully.
• BR_Failed - Failed while executing task.
• BR_Skipped - Task was skipped.

Behavior Owner (Actor)

Use BeginPlay to initialize UBehavior and ALWAYS finish the base task when the actor is destroyed.

// .h

virtual void BeginPlay() override;
virtual void Destroyed() override; // Very important

UPROPERTY(VisibleInstanceOnly, DisplayName="GameplayTasksComponent")
    class UGameplayTasksComponent* GameplayTasksComp;

UPROPERTY(EditAnywhere, BlueprintReadWrite)
    class UBehavior* Behavior;

// .cpp

void ABehaviorOwner::BeginPlay()
{
	Super::BeginPlay();

	if (!GameplayTasksComp)
	{
		GameplayTasksComp = NewObject<UGameplayTasksComponent>(this, TEXT("GameplayTasksComponent"));
		GameplayTasksComp->RegisterComponent();
	}
	Behavior = UBehavior::NewTask<UBehavior>(GameplayTasksComp);
	Behavior->ReadyForActivation();
}

void ABehaviorOwner::Destroyed()
{
	Super::Destroyed();

	if (Behavior)
		Behavior->FinishBehavior(BR_Skipped);
}

Base tasks

To setup base task, just fill Behaviors array and set Type to BT_Base inside the class constructor:

UBehHouseWork::UBehHouseWork(const FObjectInitializer& ObjectInitializer)
	: Super(ObjectInitializer)
{
	Type = BT_Base;
	Behaviors = {
		FBehaviorData(UBehWait::StaticClass(), 0, 0.2f, 100.f,0),
		FBehaviorData(UBehJerks::StaticClass(), 0, 0.5f, 0.f,0),
		// ...
	};
}

FBehaviorData Constructor:

FBehaviorData(TSubclassOf<UBehavior> InBehavior, int32 InMaxPerStage, float InRandomWeight, float InCooldown, int32 InMaxRandRepeat)
{
    Behavior = InBehavior;
    MaxPerStage = InMaxPerStage;
    RandomWeight = InRandomWeight;
    Cooldown = InCooldown;
    MaxRandRepeat = InMaxRandRepeat;
}

All _Implementation events

virtual void OnBehaviorFinished_Implementation(EBehaviorResult Result, const FString& FailedCode);

virtual void OnChildBehaviorFinished_Implementation(TSubclassOf<UBehavior> Behavior, EBehaviorResult Result, const FString& FailedCode);

virtual void OnMoveCompleted_Implementation(EPathFollowingResult::Type Result);