How to expose UObject variables from C++ to Blueprints

[Sicko_0]

As the title suggests, I’d like to know how to expose UObject variables from C++ to Blueprints in the details panel. Just like how you can expose an int or a bool by using the UPROPERTY Macro, I’d like to do the same for UObject variables such as UChildActorComponent. If I try using UPROPERTY(EditAnywhere) for a UChildActorComponent it won’t work, similarly if I also add the BlueprintReadWrite attribute it won’t appear in the details panel, although I can still access it and edit it in the blueprints. How can I go about this? Thanks!

[3dRaven]

@Sicko_0

UObject

Example uobject class

MyObject header

#pragma once

#include "CoreMinimal.h"
#include "UObject/NoExportTypes.h"
#include "MyObject.generated.h"

/**
 * 
 */
UCLASS()
class YOURPROJECT_API UMyObject : public UObject
{
	GENERATED_BODY()

public:
	UPROPERTY(EditAnywhere,BlueprintReadWrite)
	float myNumber;
};

MyObject cpp only includes header #include "MyObject.h"

Object that holds it in it’s details panel

MyActor2 header

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "MyActor2.generated.h"

UCLASS()
class LINETRACEPROJECT_API AMyActor2 : public AActor
{
	GENERATED_BODY()
	
public:	
	
	AMyActor2();

	UPROPERTY(EditAnywhere , BlueprintReadWrite, Instanced)
	class UMyObject* Obj;

};

MyActor2 cpp

#include "MyActor2.h"
#include "MyObject.h"

AMyActor2::AMyActor2()
{ 	
	PrimaryActorTick.bCanEverTick = false;
	Obj = CreateDefaultSubobject<UMyObject>(TEXT("my object"));
}

[Sicko_0]

I apologize if I am unable to understand, I’m not very experienced. But how can I do this with a USpotLightComponent for example?
I tried this but failed (it is in public):

UPROPERTY(EditAnywhere, BlueprintReadWrite, Instanced)
		class USpotLightComponent* SpotLightComponent;

[3dRaven]

It should work, I just tested it out in a scene

just be sure to initialize it in the cdo

AMyExampleClass::AMyExampleClass()
{

SpotLightComponent = CreateDefaultSubobject<USpotLightComponent>(TEXT("Spot Light Component"));
// if its in a hierarchy (as a child)
SpotLightComponent->SetupAttachment(YourParentSceneNode); // <== attach to whatever you need here 

[Sicko_0]

Ah, I didn’t initialize it. But even when I did using this code:

SceneComponent = CreateDefaultSubobject<USceneComponent>TEXT("SceneComponent"));
SetRootComponent(SceneComponent);
SpotLightComponent = CreateDefaultSubobject<USpotLightComponent>(TEXT("Spot Light Component"));

It still wouldn’t show the variable despite the Spot Light Component showing in the hierarchy.

[3dRaven]

@Sicko_0

SpotLightComponent

Add

SpotLightComponent->SetupAttachment(GetRootComponent());

and it will attach it to root. Also make sure to recompile you project (avoid the live edit tool, it doesn’t update big changes in the code)

[Sicko_0]

Still doesn’t work. I’m not sure what to do now.

[3dRaven]

Please post the code for the header and cpp file and I’ll take a look

[Sicko_0]

SecurityCamera.h:

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "Components/SpotLightComponent.h"
#include "SecurityCamera.generated.h"

UENUM(BlueprintType)
enum class ESecurityCameraType : uint8
{
	Classic UMETA(DisplayName = "Classic"),
	Night UMETA(DisplayName = "Night"),
	Thermal UMETA(DisplayName = "Thermal")
};

UCLASS()
class TESTINGGAME_API ASecurityCamera : public AActor
{
	GENERATED_BODY()
	
public:	
	ASecurityCamera();

protected:
	virtual void BeginPlay() override;

public:	
	virtual void Tick(float DeltaTime) override;

	// Security Camera
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Security Camera")
		TSet<ESecurityCameraType> CameraTypes;

	UPROPERTY(EditAnywhere, BlueprintReadOnly, Category = "Security Camera")
		int CameraGivenID;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Security Camera")
		bool IsAccessible;

	// Flashlight
	UPROPERTY(BlueprintReadOnly, Category = "Flashlight")
		bool IsFlashlightOn;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Flashlight")
		class USpotLightComponent* SpotLightComponent;

private:
	class USceneComponent* SceneComponent;
};

SecurityCamera.cpp:

#include "SecurityCamera.h"

ASecurityCamera::ASecurityCamera()
{
	PrimaryActorTick.bCanEverTick = false;
	SceneComponent = CreateDefaultSubobject<USceneComponent>(TEXT("SceneComponent"));
	SetRootComponent(SceneComponent);
	SpotLightComponent = CreateDefaultSubobject<USpotLightComponent>(TEXT("Spot Light Component"));
	SpotLightComponent->SetupAttachment(GetRootComponent());
}

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

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

[3dRaven]

You forward declared the SpotLightComponent in the header but forgot to add the include in the cpp file

your includes in SecurityCamera.cpp should look like this:

#include "SecurityCamera.h"
#include "Components/SpotLightComponent.h" 

It compiles no problem and shows up in the details panel

USpotLightComponent

Always check the needed Modules & includes

[Sicko_0]

Ah thank you! Now it works. I greatly appreciate it. It turns out its because of not initializing.