/** starts this task, should return Succeeded, Failed or InProgress
* (use FinishLatentTask() when returning InProgress)
* this function should be considered as const (don't modify state of
object) if node is not instanced! */
virtual EBTNodeResult::Type ExecuteTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory);
protected:
/** aborts this task, should return Aborted or InProgress
* (use FinishLatentAbort() when returning InProgress)
* this function should be considered as const (don't modify state of
object) if node is not instanced! */
virtual EBTNodeResult::Type AbortTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory);
public:
#if WITH_EDITOR
virtual FName GetNodeIconName() const override;
#endif // WITH_EDITOR
virtual void OnGameplayTaskDeactivated(UGameplayTask& Task) override;
/** message observer's hook */
void ReceivedMessage(UBrainComponent* BrainComp, const FAIMessage& Message);
/** wrapper for node instancing: ExecuteTask */
EBTNodeResult::Type WrappedExecuteTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory) const;
/** wrapper for node instancing: AbortTask */
EBTNodeResult::Type WrappedAbortTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory) const;
/** wrapper for node instancing: TickTask */
void WrappedTickTask(UBehaviorTreeComponent& OwnerComp, uint8*
NodeMemory, float DeltaSeconds) const;
/** wrapper for node instancing: OnTaskFinished */
void WrappedOnTaskFinished(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory, EBTNodeResult::Type TaskResult) const;
/** helper function: finish latent executing */
void FinishLatentTask(UBehaviorTreeComponent& OwnerComp, EBTNodeResult::Type TaskResult) const;
/** helper function: finishes latent aborting */
void FinishLatentAbort(UBehaviorTreeComponent& OwnerComp) const;
/** @return true if task search should be discarded when this task is selected to execute but is already running */
bool ShouldIgnoreRestartSelf() const;
/** service nodes */
UPROPERTY()
TArray<UBTService*> Services;
protected:
/** if set, task search will be discarded when this task is selected to execute but is already running */
UPROPERTY(EditAnywhere, Category=Task)
uint32 bIgnoreRestartSelf : 1;
/** if set, TickTask will be called */
uint32 bNotifyTick : 1;
/** if set, OnTaskFinished will be called */
uint32 bNotifyTaskFinished : 1;
/** ticks this task
* this function should be considered as const (don't modify state of object) if node is not instanced! */
virtual void TickTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory, float DeltaSeconds);
/** message handler, default implementation will finish latent execution/abortion
* this function should be considered as const (don't modify state of object) if node is not instanced! */
virtual void OnMessage(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory, FName Message, int32 RequestID, bool bSuccess);
/** called when task execution is finished
* this function should be considered as const (don't modify state of object) if node is not instanced! */
virtual void OnTaskFinished(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory, EBTNodeResult::Type TaskResult);
/** register message observer */
void WaitForMessage(UBehaviorTreeComponent& OwnerComp, FName MessageType)
const;
void WaitForMessage(UBehaviorTreeComponent& OwnerComp, FName MessageType, int32 RequestID) const;
/** unregister message observers */
void StopWaitingForMessages(UBehaviorTreeComponent& OwnerComp) const;
如你所见，这里有很多代码，一开始可能会有点混乱。然而，如果你已经很好地理解了蓝图，那么跳到理解C++函数应该会容易得多。例如，ExecuteTask()函数开始执行任务，但如果它返回任务仍在进行中，则不会完成任务。
以下是引擎源代码中的一条注释，可能有助于澄清这一点：
{% code lineNumbers="true" %}
```cpp
/**
* Task are leaf nodes of behavior tree, which perform actual actions
*
* Because some of them can be instanced for specific AI, following virtual functions are not marked as const:
* - ExecuteTask
* - AbortTask
* - TickTask
* - OnMessage
*
* If your node is not being instanced (default behavior), DO NOT change any properties of object within those functions!
* Template nodes are shared across all behavior tree components using the same tree asset and must store
* their runtime properties in provided NodeMemory block (allocation size determined by GetInstanceMemorySize() )
*
*/
```
{% endcode %}
我所知道的两种更好地了解如何创建C++任务的方法是：自己创建一个，或者阅读其他任务的源代码。例如，你可以阅读引擎源代码中的BTTask\_MoveTo.cpp文件，以获得关于如何创建C++任务的完整示例。不要气馁，因为使用C++很棒！
无论如何，我们将在接下来的三章中从头开始介绍创建C++任务的过程。
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