[5.2.1] SetupAttachment not working ?

Development Programming & Scripting C++
, ,
1

I have an Actor as below

UCLASS()
class AMyActor : public AActor
{
	GENERATED_BODY()

	UPROPERTY(VisibleAnywhere)
	USceneComponent* DefaultSceneRoot;

	UPROPERTY(VisibleAnywhere)
	UStaticMeshComponent* StaticMeshComp;
	UPROPERTY(VisibleAnywhere)
	USpringArmComponent* SpringArmComp;
	UPROPERTY(VisibleAnywhere)
	UCameraComponent* CameraComp;
...

};
...

AMyActor::AMyActor()
{
	PrimaryActorTick.bCanEverTick = true;

	DefaultSceneRoot = CreateDefaultSubobject<USceneComponent>("DefaultSceneRoot");
	RootComponent = DefaultSceneRoot;

	StaticMeshComp = CreateDefaultSubobject<UStaticMeshComponent>("StaticMesh");
	SpringArmComp = CreateDefaultSubobject<USpringArmComponent>("SpringArm");
	CameraComp = CreateDefaultSubobject<UCameraComponent>("Camera");

	StaticMeshComp->SetupAttachment(DefaultSceneRoot);
	SpringArmComp->SetupAttachment(DefaultSceneRoot);
	CameraComp->SetupAttachment(SpringArmComp);
}

The actor is inherited by blueprint and created in scene

image In scene attachment hierarchy

but it seems only the root component got set properly. All attached components were detached.

am I doing any thing wrong?