Unreal Engine, from C++ spawn Blueprint inherited from C++ class, very small example

Prepare Project

Create Project

• Games / Blank
  • C++
  • Desktop
  • Maximum
  • Starter Content: no
  • Raytracing: no
  • Location: your choice
  • Project Name: ShowActor
• Create

Change Map to Basic

When the UE-Editor is open:

• File / New Level / Basic / Create
• File / Save Current Level as ... / Basic01
• Edit / Project Settings / Maps & Modes / Editor Startup Map: Basic01
• Edit / Project Settings / Maps & Modes / Editor Game Default Map: Basic01

Create Classes

Actor

• Tools / New C++ Class
  • Parent Class: Actor
  • Name MiniActor
  • Create Class

Header File: MiniActor.h

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "MiniActor.generated.h"

UCLASS(Blueprintable)
class SHOWACTOR_API AMiniActor : public AActor
{
  GENERATED_BODY()
	
public:	

	AMiniActor();

protected:

  virtual void BeginPlay() override;

  UPROPERTY(EditAnywhere, Category = "Structure", meta = (DisplayName = "Mesh"))
  UStaticMesh* m_pMesh;

  UPROPERTY(EditAnywhere, Category = "Structure", meta = (DisplayName = "Scene Component Root"))
  USceneComponent* m_pScRoot;

  UPROPERTY(EditAnywhere, Category = "Structure", meta = (DisplayName = "Static Mesh Component of Root"))
  UStaticMeshComponent* m_pSmcRoot;
};

Source File

#include "MiniActor.h"

AMiniActor::AMiniActor()
{
	m_pScRoot = CreateDefaultSubobject<USceneComponent>("Root");
	RootComponent = m_pScRoot;

	m_pSmcRoot = CreateDefaultSubobject<UStaticMeshComponent>("SmcRoot");

	FAttachmentTransformRules transformRule = FAttachmentTransformRules::SnapToTargetIncludingScale;
	m_pSmcRoot->AttachToComponent(RootComponent, transformRule);

	PrimaryActorTick.bCanEverTick = false;
}

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

	if (m_pMesh != nullptr)
	{
		m_pSmcRoot->SetStaticMesh(m_pMesh);
	}
}

Build

Now build the project. Nothing works so don't even try to test it in the UE-Editor, but the code should compile and link. This is a class that is complete as it is.