I wonder why it gets null pointer

Development Programming & Scripting C++
,
1

TestWidget.h

class Something_API UTestWidget : public
{
	// 
	void Func();

	class ATComponent* OwningComponent;
	//
};

TestWidget.cpp

void UTestWidget::Func()
{
	if(OwningComponent != nullptr)
	{
		OwningComponent->DoSomething();
	}
}

TComponent.h

class Something_API ATComponent : public APlayerComponent
{
	//
	void BeginPlay() override;
	void DoSomething();
	class ATestWidget TheWidget;
	//
}

TComponent.cpp

void ATComponent::BeginPlay()
{
	//
	TheWidget = CreateWidget<UTestWidget>(UGameplayStatics::GetPlayerController(GetWorld(), 0), UTestWidget::StaticClass());
	
	if(TheWidget != nullptr){
	TheWidget->OwningComponent = this;
	}
	//
}

void ATComponent::DoSomething()
{
	GEngine->AddOnScreenDebugMessage(-1, 5.0f, FColor::Red, TEXT("ATComponent::DoSomething("));
}

There was no problem in compilation. But after I access ATComponent::DoSomething through UTestWidget::Func(), Unreal Engine throws EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000000. Even I prevented the nullptr.
Is there any good solution to declare the pointer right or fix the bug?

Thank you for reading my trouble.

2

If you run it in Debugger, it will tell you what’s failing.

3

looks like something is not assigning well there…
try to debug TheWidget->OwningComponent, may it be nullptr…

1 Like
4

Thank you so much for your help.
I found out the cause. After i write UPROPERTY() on the raw pointer, there’s no more nullptr error.
I think the pointer is garbage-collected or destroyed by something like it.

1 Like