Can't access to widget second time

[EzioMercer]

I have a AScoreboardWidget

ScoreboardWidget.h

#pragma once

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

UCLASS()
class FLY_BIRD_FLY_API AScoreboardWidget : public AActor {
	GENERATED_BODY()

	public:
		// Sets default values for this actor's properties
		AScoreboardWidget();

	protected:
		// Called when the game starts or when spawned
		virtual void BeginPlay() override;

	public:
		// Called every frame
		virtual void Tick(float DeltaTime) override;

		void SetScore(int Score);

	private:
		UPROPERTY(EditDefaultsOnly, Category = "Category")
		class UUserWidget* Scoreboard;

};

ScoreboardWidget.cpp

// Fill out your copyright notice in the Description page of Project Settings.

#include "ScoreboardWidget.h"
#include "Blueprint/UserWidget.h"
#include "Components/TextBlock.h"
#include "Internationalization/Text.h"

// Sets default values
AScoreboardWidget::AScoreboardWidget() {
	// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
	PrimaryActorTick.bCanEverTick = true;
}

// Called when the game starts or when spawned
void AScoreboardWidget::BeginPlay() {
	Super::BeginPlay();

	Scoreboard->AddToViewport();

	Cast<UTextBlock>(Scoreboard->GetWidgetFromName(TEXT("ScoreText")))->SetText(
		FText::FromString("Score is: 0")
	);
}

// Called every frame
void AScoreboardWidget::Tick(float DeltaTime) {
	Super::Tick(DeltaTime);
}

void AScoreboardWidget::SetScore(int Score) {
	UE_LOG(LogTemp, Warning, TEXT("Score: %d"), Score);
	
	if (auto x = Scoreboard) {
		UE_LOG(LogTemp, Warning, TEXT("Scoreboard found"));
	} else {
		UE_LOG(LogTemp, Warning, TEXT("Scoreboard not found"));

		return;
	}

	if (auto x = Scoreboard->GetWidgetFromName(TEXT("ScoreText"))) {
		UE_LOG(LogTemp, Warning, TEXT("Widget found"));
	} else {
		UE_LOG(LogTemp, Warning, TEXT("Widget not found"));

		return;
	}
	
	Cast<UTextBlock>(Scoreboard->GetWidgetFromName(TEXT("ScoreText")))->SetText(
		FText::FromString("Score is: 1")
	);

	// Cast<UTextBlock>(Scoreboard->GetWidgetFromName(TEXT("ScoreText")))->SetText(
	// 	FText::FromString(
	// 		FString::Printf(TEXT("Score is: %d"), Score)
	// 	)
	// );
}

Also I have a ABird class which uses this widget

Bird.h

...
public:
		...
		void SetScore(int NewScore);

private:
		...
		UPROPERTY(EditDefaultsOnly, Category = "Components")
		TSubclassOf<AScoreboardWidget> ScoreboardWidget;
...

Bird.cpp

...
void ABird::SetScore(int NewScore) {
	Score = NewScore;
	UE_LOG(LogTemp, Warning, TEXT("Score: %d"), Score);
	ScoreboardWidget->GetDefaultObject<AScoreboardWidget>()->SetScore(Score);
}
...

Here is more info on screenshots:

So as you can see I can access to widget inside of BeginPlay but not inside of SetScore. What is the problem?

[PREDALIEN]

In AScoreboardWidget BeginPlay you need to create the widget and then add it to the viewport.

AScoreboardWidget:

UPROPERTY(EditAnywhere)
TSubclassOf<UUserWidget> ScoreboardClass;
UUserWidget* ScoreboardWidget;

//BeginPlay
ScoreboardWidget = UWidgetBlueprintLibrary::Create(this, ScoreboardClass, GetWorld()->GetFirstPlayerController());
ScoreboardWidget->AddToViewport();

Set ScoreboardClass in you blueprint child in AScoreboardWidget.

Then you need a reference to the AScoreboardWidget Actor in your ABird.
ABird:

UPROPERTY(EditAnywhere)
AScoreboardWidget* WidgetActor;

// SetScore function
WidgetActor->SetScore(Score)

You definitely need to set a specific AScoreboardWidget actor (via the detail panel on the level or UGameplayStatics::GetActorOfClass).

[EzioMercer]

But already have a widget. You can see in screenshots that I’m able to interact with it inside BeginPlay method. The text “Score is: 0” is from this method

[PREDALIEN]

In ABird you take GetDefaultObject - this is an engine object that stores the default values ​​of class variables. You should not use it as an object that can be used at runtime.

At runtime you need to create a new widget instance as described above.

To be honest, I’m surprised you managed to use it the first time. It’s not supposed to work like that.

[EzioMercer]

I’m really sorry to bothering you. But if you don’t mind can we please continue discussing? I don’t understand a several things:

1. I used GetDefaultObject because I saw a lot of time that using TSubclassOf is more safety and help in editor to choose correct object. BUT when I use this I can’t access to the methods and variables of desired class. Because of this I started using GetDefaultObject everywhere to access members which I need. What is an alternative way to do it?
2. Also you says that it is engine object and it just stores the default values BUT I used it a lot of time and didn’t get any errors till yesterday. Also when I used it in other places I correctly got the need objects which I define from Editor so I don’t understand how does it work?
3. I still can’t understand why I can access the widget inside Scoreboard in BeginPlay but can’t get access to widget inside Scoreboard in SetScore? In which moment I loose the widgets which is defined inside Scoreboard?

Sorry if they are stupid questions but I can’t understand the core concepts

[PREDALIEN]

Class - is the plan according to which the objectwill be built.
You can create one class, and then create countless objects (instances of the class).

After creating an object - you can access their variables and functions.

TSubclassOf as the name suggests, it allows you to select a CLASS that is a child of the specified one. In your case, it is a child class of UUserWidget.
Then you need to use this to create objects of selected class.

In C++, once the source code is compiled - you cannot change the class. You can only change the objects from which they were created.
But you can create a blueprint based on a C++ class.
That’s why Epic Games came up with CDO (Class Default Object) - an object in which you change the values ​​when you edit a class in Blueprint.
You can get a CDO and simulate its change similar to how you do it in blueprint, but this should only be used during development, not runtime.

When you change a CDO you need to regenerate the class (compile the blueprint). After the class is generated, a new CDO is also created.
When you run PIE all blueprints are compiled automatically. Probably when PIE is already running - this happens too.
Objects created based on an old class break because their class is no longer valid.
Apparently this is exactly what happens after you call SetText.

[EzioMercer]

So If I understood you correctly, when I create a widget in editor like this:

I create a CLASS and not the object which I can interact directly?

It is a little bit strange because I thought I already created a widget I don’t wanna to create it again from C++ I just need a reference to this

[EzioMercer]

I found this video which I think talking exactly what did you mean

Now I can understand you more

I just thought that I can create widget just in editor and then interact with it but now I see that I have to create a CLASS by myself and create a widget based on this CLASS

I’m still a little confused because in my mind it must be legal to work with widget created by editor directly without recreating it in C++

BTW Thank you so much for your time