# Pointer to subobject gets invalid after creation

**URL:** <https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833>\
**Category:** Programming & Scripting\
**Tags:** unreal-engine\
**Created:** [August 2, 2018, 8:09pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833 "2018-08-02T20:09:01Z")\
**Posts on this page:** 20\
**Page:** 1

<div class="post-metadata">

**Author:** ![Kurtaa1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Kurtaa1](https://forums.unrealengine.com/u/Kurtaa1)\
**Post date:** [August 2, 2018, 8:09pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/1 "2018-08-02T20:09:01Z")

</div>

Hi! I am making a class derived from Character. This class creates an instance of a “Cover Helper” Class (derived from Scene Component) using createDefaultSubobject(). The problem is that this Cover Helper instance becomes invalid for some reason which hinders me from using it’s function findCoverNear(). I checked if it is valid using IsValid() on several different occasions, in the constructor, in BeginPlay() and in Tick(). I also check via Blueprints through a Blueprint class derived from my custom character class. Only the check inside the constructor comes back as valid. I don’t understand how this can happen! It have been looking around the internet but can’t seem to find any solution, help would be much appreciated! source and header files pasted below

my custom character class (.cpp):

```
#include "AdvancedCharacter.h"

// Sets default values
AAdvancedCharacter::AAdvancedCharacter(const FObjectInitializer& ObjectInitializer)
	: Super(ObjectInitializer.SetDefaultSubobjectClass<UAdvCharMovementComponent>(ACharacter::CharacterMovementComponentName))
{
	if (GEngine) { GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Yellow, TEXT("test")); }
	//MovementComponent = Cast<UAdvCharMovementComponent>(GetMovementComponent());
	CoverHelper = CreateDefaultSubobject<UCoverHelper>(TEXT("CoverHelperObject"));
	CoverHelper->SetupAttachment(RootComponent);
	if (IsValid(CoverHelper))
	{
		if (GEngine) { GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Blue, TEXT("isValid")); }
	}
	else {
		if (GEngine) { GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Blue, TEXT("notValid")); }
	}
	
 	// Set this character 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 AAdvancedCharacter::BeginPlay()
{
	Super::BeginPlay();
	if (IsValid(CoverHelper))
	{
		if (GEngine) { GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Green, TEXT("isValid")); }
	}
	else {
		if (GEngine) { GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Green, TEXT("notValid")); }
	}
}

// Called every frame
void AAdvancedCharacter::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);
	
	if (IsValid(CoverHelper))
	{
		if (GEngine) { GEngine->AddOnScreenDebugMessage(1, 2.0f, FColor::Red, TEXT("isValid")); }
	}
	else {
		if (GEngine) { GEngine->AddOnScreenDebugMessage(1, 2.0f, FColor::Red, TEXT("notValid")); }
	}
}

// Called to bind functionality to input
void AAdvancedCharacter::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent)
{
	Super::SetupPlayerInputComponent(PlayerInputComponent);

}
UCoverHelper *AAdvancedCharacter::GetCoverHelper()
{
	return CoverHelper;
}

```

custom character class (.h)

```
#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Character.h"
#include "AdvCharMovementComponent.h"
#include "CoverHelper.h"
#include "AdvancedCharacter.generated.h"

UCLASS()
class ADVCHARPROJ_API AAdvancedCharacter : public ACharacter
{
	GENERATED_UCLASS_BODY()

	

public:
	UPROPERTY(VisibleAnywhere, BlueprintReadOnly ,BlueprintGetter = "GetCoverHelper")
		class UCoverHelper *CoverHelper;

	UFUNCTION(BlueprintGetter)
		UCoverHelper *GetCoverHelper();

protected:
	// Called when the game starts or when spawned
	virtual void BeginPlay() override;
	
public:	
	// Called every frame
	virtual void Tick(float DeltaTime) override;

	// Called to bind functionality to input
	virtual void SetupPlayerInputComponent(class UInputComponent* PlayerInputComponent) override;
	
	UAdvCharMovementComponent *MovementComponent;
	
};

```

CoverHelper.cpp:

```
#include "CoverHelper.h"

// Sets default values for this component's properties
UCoverHelper::UCoverHelper()
{
	// Set this component to be initialized when the game starts, and to be ticked every frame. You can turn these features
	// off to improve performance if you don't need them.
	PrimaryComponentTick.bCanEverTick = true;
	//isActive = false;
	CharacterOwner = this->GetAttachmentRootActor();
	//UAdvCharMovementComponent *MovementComponent = Cast<UAdvCharMovementComponent>(CharacterOwner->GetMovementComponent());
	// ...
}

// Called when the game starts
void UCoverHelper::BeginPlay()
{
	Super::BeginPlay();

	// ...
	
}

// Called every frame
void UCoverHelper::TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction* ThisTickFunction)
{
	Super::TickComponent(DeltaTime, TickType, ThisTickFunction);

	// ...
}

bool UCoverHelper::FindCoverNearest(float range) 
{
	bool validCover = false;
	FVector startLocation = CharacterOwner->GetActorLocation();
	FHitResult prevHit;
	FCollisionQueryParams CollisionParams;
	CollisionParams.AddIgnoredActor(CharacterOwner);
	for (int i = 0; i < 8; i++) {
		if (GEngine) { GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Yellow, TEXT("for")); }
		FRotator rot = FRotator(0, i * 45,0);
		FHitResult Hit;
		FVector direction = FVector(range, 0, 0);
		FVector endLocation = startLocation + rot.RotateVector(direction);
		validCover = GetWorld()->LineTraceSingleByChannel(Hit, startLocation, endLocation, ECollisionChannel::ECC_WorldDynamic, CollisionParams);
		DrawDebugLine(GetWorld(), startLocation, endLocation, FColor::Green, true, -1, 0, 2.f);
		if (validCover) {
			if (GEngine) { GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Yellow, TEXT("validCover")); }
			float dist = Hit.Distance;
			if (prevHit.bBlockingHit) {
				prevHit = Hit;
			}
			else if (Hit.Distance < prevHit.Distance) {
				prevHit = Hit;
			}
		}
		
	}
	return validCover;
}
bool UCoverHelper::FindCoverDirectional(FQuat direction, float range)
{
	bool validCover = false;
	//raycast logic
	return validCover;
}

void UCoverHelper::SetIsActive(bool b) 
{
	//isActive = b;
}

bool UCoverHelper::GetIsActive()
{
	return false;
}

```

CoverHelper.h:

```
#pragma once

#include "CoreMinimal.h"
#include "EngineGlobals.h"
#include "Components/SceneComponent.h"
#include "AdvancedCharacter.h"
#include "DrawDebugHelpers.h"
#include "CoverHelper.generated.h"

UCLASS( ClassGroup=(Custom), meta=(BlueprintSpawnableComponent) )
class ADVCHARPROJ_API UCoverHelper : public USceneComponent
{
	GENERATED_BODY()

public:	
	// Sets default values for this component's properties
	UCoverHelper();
	AActor *CharacterOwner;
protected:
	// Called when the game starts
	virtual void BeginPlay() override;

public:	
	// Called every frame
	virtual void TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction* ThisTickFunction) override;

	UFUNCTION(BlueprintCallable)
	bool FindCoverNearest(float range);
	bool FindCoverDirectional(FQuat direction, float range);
	void SetIsActive(bool b);
	bool GetIsActive();
		
	
};

```

---

<div class="post-metadata">

**Author:** ![dZh0](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@dZh0](https://forums.unrealengine.com/u/dZh0)\
**Post date:** [August 2, 2018, 8:46pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/2 "2018-08-02T20:46:54Z")

</div>

I haven’t looked in-depth through your code but…

Shouldn’t line 18 from your “custom character class (.h)” read:

```
UCoverHelper *CoverHelper;

```

…without the class declaration?

---

<div class="post-metadata">

**Author:** ![Kurtaa1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Kurtaa1](https://forums.unrealengine.com/u/Kurtaa1)\
**Post date:** [August 2, 2018, 9:38pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/3 "2018-08-02T21:38:26Z")

</div>

It probably should. I added “class” because I read it somewhere and it fixed an error I had. Now when I remove it it doesn’t seem to make a difference.

---

<div class="post-metadata">

**Author:** ![Balgy](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Balgy](https://forums.unrealengine.com/u/Balgy)\
**Post date:** [August 3, 2018, 12:12am UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/4 "2018-08-03T00:12:41Z")

</div>

Perhaps the problem is not in the creation of the subobject but on the `IsValid()` check. IsValid() is not just a null check, it has a couple of extra stuff.

Try using a normal `if` check instead of your `IsValid()` assertion.

---

<div class="post-metadata">

**Author:** ![Kurtaa1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Kurtaa1](https://forums.unrealengine.com/u/Kurtaa1)\
**Post date:** [August 3, 2018, 8:29am UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/5 "2018-08-03T08:29:15Z")

</div>

That does not seem to be the problem. The normal if check also returns a nullpointer

---

<div class="post-metadata">

**Author:** ![dZh0](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@dZh0](https://forums.unrealengine.com/u/dZh0)\
**Post date:** [August 3, 2018, 12:43pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/6 "2018-08-03T12:43:52Z")

</div>

What do you mean by “it doesn’t seem to make a difference”?

You removed the “class” keyword. The code compiled. `IsValid(CoverHelper)` returns:

- **true** in `AAdvancedCharacter()` - the constructor
- **false** in `BeginPlay()`
- **false** in `Tick()`

Is all this correct?

P.S. I would really love to see where you read about this kind of declaration. What problem did it solve?

---

<div class="post-metadata">

**Author:** ![Kurtaa1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Kurtaa1](https://forums.unrealengine.com/u/Kurtaa1)\
**Post date:** [August 3, 2018, 1:45pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/7 "2018-08-03T13:45:40Z")

</div>

What I mean is that no issues were solved or caused by removing the class declaration. The code ran the same.  
Yes all that is correct.  
I can’t remember where I read it. Since I have been having alot of issues with the engine lately I have been looking a little bit all over the place for solutions. I think it was some sort of “undefined identifier” compiler error but I am not sure.

---

<div class="post-metadata">

**Author:** ![dZh0](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@dZh0](https://forums.unrealengine.com/u/dZh0)\
**Post date:** [August 6, 2018, 7:59am UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/8 "2018-08-06T07:59:26Z")

</div>

I got deeper in this bizarre declaration and it turns out it is called [Elaborated Type Specifier](https://en.cppreference.com/w/cpp/language/elaborated_type_specifier).

You don’t need it but it should not affect the execution. Something else is nullifying your pointer.

Add a Data Breakpoint to your pointer and see what clears it. It might be a blueprint or some other part of your code.

---

<div class="post-metadata">

**Author:** ![Kurtaa1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Kurtaa1](https://forums.unrealengine.com/u/Kurtaa1)\
**Post date:** [August 6, 2018, 5:27pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/9 "2018-08-06T17:27:14Z")

</div>

I tried adding a Data Breakpoint to the CoverHelper variable but when it breaks it says “Source not Available” I have never used the Debugger in Unreal before and I don’t know how to solve this.

---

<div class="post-metadata">

**Author:** ![dZh0](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@dZh0](https://forums.unrealengine.com/u/dZh0)\
**Post date:** [August 6, 2018, 7:41pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/10 "2018-08-06T19:41:36Z")

</div>

Well I had to try it out…

It runs fine on my build (4.20.1):

![249662-valid.png](https://d3kjluh73b9h9o.cloudfront.net/original/4X/4/a/9/4a965681fa158b900e71f7b8390edc79f680eea8.png)

Of course I had to replace your `UAdvCharMovementComponent` with the default `UCharacterMovementComponent` but I did nothing more than that. (copy/pasted all other code)

My best guess is that you nullify your pointer in your `UAdvCharMovementComponent` or some other class that has access to it.

The code posted on the question is fine.

---

<div class="post-metadata">

**Author:** ![Kurtaa1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Kurtaa1](https://forums.unrealengine.com/u/Kurtaa1)\
**Post date:** [August 9, 2018, 7:24pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/11 "2018-08-09T19:24:17Z")

</div>

hmm that’s wierd I don’t think there is any other class that has access to the CoverHelper class. I tried replacing the UAdvCharMovementComponent with the default UCharacterMovementComponent class, like you, but no luck. This is really funky, should I try reinstalling the engine or something? This project was migrated from 4.18 to 4.20 could that have an affect?

---

<div class="post-metadata">

**Author:** ![dZh0](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@dZh0](https://forums.unrealengine.com/u/dZh0)\
**Post date:** [August 9, 2018, 8:27pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/12 "2018-08-09T20:27:16Z")

</div>

I have no idea if the build has anything in common but it rarely does.

Try it out on a new project with the default movement component and tell us how it went.

It takes 30 min at most.

---

<div class="post-metadata">

**Author:** ![Kurtaa1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Kurtaa1](https://forums.unrealengine.com/u/Kurtaa1)\
**Post date:** [August 13, 2018, 4:27pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/13 "2018-08-13T16:27:57Z")

</div>

Hi I tried what you said and it seems that it is the line `UFUNCTION(BlueprintCallable)` in Coverhelper.h before the `findCoverNearest` method that somehow nullifies my coverhelper. I came to this conclusion by adding one small part of code at a time and se when the result gives me an invalid result. Once it got invalid I had to undo the change in code and close the editor and delete the generated project files and rebuild the project in order to get valid again. So something fishy seems to happen in the binaries ,when I add that line of code, that is not resolved after a hot reload.

---

<div class="post-metadata">

**Author:** ![dZh0](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@dZh0](https://forums.unrealengine.com/u/dZh0)\
**Post date:** [August 14, 2018, 1:35pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/14 "2018-08-14T13:35:52Z")

</div>

It can’t believe **UFUNCTION** is the problem.

I am starting to think that you don’t attach your **CoverHelper** correctly in _AdvancedCharacter.cpp_ and it’s swiped up by the garbage collector. (unattached components are automatically deleted)

I don’t see where **RootComponent** is set. The variable itself comes from **AActor** but its content is constructed in **ACharacter**.

Can you check if **RootComponent** is valid in _AdvancedCharacter.cpp_ before attaching CoverHelper to it?

---

<div class="post-metadata">

**Author:** ![Kurtaa1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Kurtaa1](https://forums.unrealengine.com/u/Kurtaa1)\
**Post date:** [August 14, 2018, 1:59pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/15 "2018-08-14T13:59:31Z")

</div>

The RootComponent seems to be valid before and after I attach the CoverHelper. What content excactly needs to be constructed?

---

<div class="post-metadata">

**Author:** ![dZh0](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@dZh0](https://forums.unrealengine.com/u/dZh0)\
**Post date:** [August 14, 2018, 8:27pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/16 "2018-08-14T20:27:41Z")

</div>

The **RootComponent** of an **ACharacter** is an **UCapsuleComponent**. Your class is derived from it so the constructor of **ACharacter** should create the capsule and assign it to the root.

Can you check `IsValid(CoverHelper->GetAttachParent())` instead of RootComponent?

(long shot but I’m running out of ideas)

---

<div class="post-metadata">

**Author:** ![ekicam2](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@ekicam2](https://forums.unrealengine.com/u/ekicam2)\
**Post date:** [August 15, 2018, 5:27pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/17 "2018-08-15T17:27:04Z")

</div>

As far as I can see you are missing a lot UPROPERTY() tags above pointers. That could mean that the CoverHelper instance is deleted by the GC as a result of the references. Rule of thumb always mark your pointers as UPROPERTY **always**.

You can read more about garbage collection here:

> **[A new, community-hosted Unreal Engine Wiki](https://forums.unrealengine.com/t/a-new-community-hosted-unreal-engine-wiki/141494)**
>
> After over a year in maintenance mode, the official Unreal Engine Wiki is now permanently offline. These resources now live on a new community-run Unreal Engine Community Wiki — ue4community.wiki! You will be able to find content from the official...

---

<div class="post-metadata">

**Author:** ![ekicam2](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@ekicam2](https://forums.unrealengine.com/u/ekicam2)\
**Post date:** [August 15, 2018, 5:36pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/18 "2018-08-15T17:36:47Z")

</div>

It’s shorten version for standard _forward declaration_.  
Simply instead of writing:

```
class Foo;

Foo* SomeVariable;

```

you are just typing:

```
class Foo* SomeVariable;

```

It helps us because we don’t need to include whole header file to another header.  
C++ needs to know size of the member and if it’s a pointer, the size will be always same on a specific platform!  
And why is that so useful you may ask, because it prevents us from circular dependencies.

---

<div class="post-metadata">

**Author:** ![dZh0](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@dZh0](https://forums.unrealengine.com/u/dZh0)\
**Post date:** [August 15, 2018, 6:27pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/19 "2018-08-15T18:27:07Z")

</div>

At the end I thought that it could be a GC cleanup but I never knew that UPROPERTY() is so important.

Thanks for the useful link. I hope @Kurtaa1 tries this.

---

<div class="post-metadata">

**Author:** ![Kurtaa1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Kurtaa1](https://forums.unrealengine.com/u/Kurtaa1)\
**Post date:** [August 17, 2018, 6:11pm UTC](https://forums.unrealengine.com/t/pointer-to-subobject-gets-invalid-after-creation/430833/20 "2018-08-17T18:11:51Z")

</div>

It randomly started working again, I don’t know how long it will last though since Unreal has been behaving very strange lately. I think that this might have been the issue though( it seems like the most reasonable explaination). Thank you very much for the article. It gave me much better insight to C++ with Unreal 🙂