Crashing when accessing fields within a method defined in C++

Development Programming & Scripting
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1

I am currently having trouble accessing a field from a method that is defined in a class. It will fail to access and return a null pointer. I am fairly new with C++ so I may be screwing this up and require some help understanding what is going on.

I have defined a C++ Character Script that contains a field FirstPersonCamera as follows
In the header file:

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Character.h"
#include "Camera/CameraComponent.h"
#include "PACombatInterface.h"
class UCharacterMovementComponent;
class UCapsuleComponent;
#include "PACharacter.generated.h"

UCLASS(Blueprintable)
class UNTITLEDGAMEPROJECT_API APACharacter : public ACharacter, public IPACombatInterface
{
	GENERATED_BODY()

public:
	// Sets default values for this character's properties
	APACharacter();

	UPROPERTY(EditAnywhere, BlueprintReadOnly)
	USkeletalMeshComponent *FirstPersonMesh;

	UPROPERTY(EditAnywhere, BlueprintReadOnly)
	UCameraComponent *FirstPersonCamera;

// ... etc ...

And it’s initialized in the C++ file as follows:

// ... etc ...

	FirstPersonCamera = CreateDefaultSubobject<UCameraComponent>(TEXT("First Person Camera"));
	FirstPersonCamera->SetupAttachment(RootComponent);
	FirstPersonCamera->SetRelativeLocation(FVector(0.0, 0.0, BaseEyeHeight));
	FirstPersonCamera->bUsePawnControlRotation = true;

// ... etc ...

Inside this the c++ implementation I have a QueryMountable method which accesses the FirstPersonCamera to get the rotation as follows:

In the Header:

// ... etc ...

protected:
	UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "Events")
	bool QueryMountable(float QueryDistance, FVector &MountLocation);

// ... etc ...

And in the C++ file as follows:

// ... etc ...
bool APACharacter::QueryMountable_Implementation(float QueryDistance, FVector &MountLocation)
{
	if(bIsCrouched) {
		return false;
	}
	FHitResult HitResult;
	FCollisionQueryParams Params = FCollisionQueryParams::DefaultQueryParam;
	Params.AddIgnoredActor(this);
	if(!FirstPersonCamera)
	{
		GEngine->AddOnScreenDebugMessage(-1, 1, FColor::Red, "FirstPersonCamera is NULL");
		return false;
	}
// ... etc ...

This method works if the player is currently possessing the character. I do not get the error. However, when the character is possessed by an AI and tries to use this method, the error is printed out. My current code avoids crashing, however I do want my AI to be able to use this mount method. I am not sure why the First Person Camera in this case would return NULL considering that it is initialized in the constructor.

PLEASE NOTE IF RELEVANT: in the engine I have created a blueprint class based off this C++ class. However, I am only using it to set the variables for the mesh and AI controller that is calling this QueryMount function. This Blueprint class is inheriting from a C++ child class of the above class. However again this is only creating some variables that I require for the AI Controller to access. it doesn’t even have a C++ implementation file, only a header file

C++CharacterClass → C++EnemyClass → Blueprint Class

2

EditAnywhere can cause blueprint corruption when used with components. I use VisibleAnywhere. See if it happens if you create a new blueprint asset. after changing to VisibleAnywhere.

It’s in the c++ constructor right?

I don’t see anything else right now. I doubt the entire camera component would be “optimized away” while an AI uses the pawn.

Here’s another corruption case (the property / compnent name got stuck), this is present in all engine versions afaik:

https://stackoverflow.com/questions/54580713/my-camera-pointer-is-returning-null-when-accessing-the-camera-anywhere-else-but

But, that doesn’t explain why it would work for a player, not an npc. Blueprints just misbehave often and I want to rule out that possibility.