NEED HELP!!! BP Actor can't inherit Cpp Actor data that Create by Constructor Method

Development Programming & Scripting C++
1

Hello, Every one.

Recently I have a problem, It occurs when BP Actor inherited from My C++ Actor.

I wirte a App Actor, like this:



// .h file
UCLASS()
class COSMOS_API MyCppActor: public AActor
{
	GENERATED_BODY()

	static FName BackName;
public:
	UPROPERTY(Category = TestCG, VisibleAnywhere, BlueprintReadWrite)
	USceneComponent* Root;
	UPROPERTY(Category = TestCG, VisibleAnywhere, BlueprintReadWrite)
	class UStaticMeshComponent* Back;
public:	
	MyCppActor();
	virtual void BeginPlay() override;
	virtual void Tick( float DeltaSeconds ) override;
};


// .cpp file
FName MyCppActor::BackName(TEXT("BackMesh"));

MyCppActor::MyCppActor()
{
	PrimaryActorTick.bCanEverTick = true;
	Root = CreateDefaultSubobject<USceneComponent>(TEXT("MyRoot"));
	UStaticMesh* TmpMesh = nullptr;
	UMaterialInterface* TmpMat = nullptr;
	UMaterialInstanceDynamic* tmpMID = nullptr;

	if (Root)
	{
		Back = CreateDefaultSubobject<UStaticMeshComponent>(MyCppActor::BackName);
		Back->bCastDynamicShadow = false;
		//	load mesh from plugin Meshes dir and set to Back(an UStaticMeshComponent*)
		TmpMesh = DSUtility::LoadMeshFromPath(TEXT("/MyTestPlugin/Meshes/Back"));
		Back->SetStaticMesh(TmpMesh);
		//	load material from plugin Materials dir
		TmpMat = DSUtility::LoadMatFromPath(TEXT("/MyTestPlugin/Materials/Back"));
		
		//	create material instance and set to mesh
		tmpMID = Back->CreateAndSetMaterialInstanceDynamicFromMaterial(0, TmpMat);
		Back->AttachParent = Root;
	}

	RootComponent = Root;
}

void MyCppActor::BeginPlay()
{
	Super::BeginPlay();	
}

void MyCppActor::Tick( float DeltaTime )
{
	Super::Tick( DeltaTime );
}

In Editor, when I created an Cpp MyActor instance into scene, there is no problem, all right.

But, if I create a new BP Actor(MyBpActor) inherit from CPP Actor(MyCppActor) and create instance from BP Actor(MyBpActor), There will be problems.
I can’t see any material instance on Back(UStaticMeshComponent).

May I ask why? and How to solve this problem?

thank you.

2

Not sure if this solves it. But try calling super constructor from your BP.

3

Hi there! My only guess is that the BP inherited instance is calling the constructor with an FObjectInitializer instead of your constructor. This is being generated by the GENERATED_BODY() macro. If you want to implement your own constructor, use GENERATED_UCLASS_BODY() instead of the GENERATED_BODY() macro. Then, implement your constructor that takes a const FObjectInitializer, for example:

MyCppActor(const class FObjectInitializer& ObjectInitializer);

In your implementation, you’ll want to make sure you call the parent’s constructor as well. See this doc for more details: Gameplay Classes in Unreal Engine | Unreal Engine 5.1 Documentation

4

trying using

UCLASS(Blueprintable)