Game crashes after implementation of Tick function

Development Programming & Scripting
1

Can you run this by playing from Visual Studio, so when the exception is thrown it shows you exactly where it crashes?

2

FollowCamera could be null.

3

The problem is that, on the last line, you are using

Controller->CurrentInteractable = nullptr;

But you never check for a not null variable (the check is on an if, but this is outside the scope of that), so what happens is that you are doing this

Controller is null => nullptr->CurrentInteractable = nullptr //ACCESS VIOLATION

The solution is to simply use this

if(Controller)
    Controller->CurrentInteractable = nullptr;

or simply, after you CAST the controller, return if is not the type you need (because you cannot do anything else). On the very first line of code put this:

//Early out
AGameplayController* Controller = Cast<AGameplayController>(GetController());
if(!Controller)
    return;

Cheers!

4

Hi !

I’m following a tutorial in YouTube to create an inventory system ( here, it’s the tutorial : Crafting/Inventory System Tutorial in Unreal Engine - #1 - YouTube).

I’m in the second video and after implementing the function to detect if we have an object in front of us and put it in Tick, my game crash. I do not really understand what I have done wrong since I am the tutorial step by step (twice same) and I am always confronted with this problem. So I ask for your help because I am a bit overwhelmed.

Here is the code of the functions in question :

void AElyosaCharacter::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);
	CheckForInteractables();
}

void AElyosaCharacter::CheckForInteractables()
{

	FHitResult HitResult;

	FVector StartTrace = FollowCamera->GetComponentLocation();
	FVector EndTrace = (FollowCamera->GetForwardVector() * 300) + StartTrace;

	FCollisionQueryParams QueryParams;
	QueryParams.AddIgnoredActor(this);

	AGameplayController* Controller = Cast<AGameplayController>(GetController());


	if (GetWorld()->LineTraceSingleByChannel(HitResult, StartTrace, EndTrace, ECC_Visibility, QueryParams) && Controller)
	{

		//Check if the item we hit was a interactable item
		if (AInteractable* Interactable = Cast<AInteractable>(HitResult.GetActor()))
		{
			Controller->CurrentInteractable = Interactable;
			return;
		}

	}

	//If we didn't hit anything, or the thing we hit was not a interactable, set the currentinteractable to nullptr
	Controller->CurrentInteractable = nullptr;

}

I would like to make it work but more important for me, to understand why there is this problem ! I really want to understand after all the hours I spent on it.

Maybe you need more information. If so, ask me what you need and I will reply as soon as possible !

Thank you for taking the time to read this message! You are awesome and I hope you can help me!

5

Hi,

Thank’s for your fast reply and your clear explication !

So I did what you told me to do and the program stop at this line Controller->CurrentInteractable = nullptr; with the exception : Access violation writing (It is a translation may be bad, I forgot to change the language of my IDE in English). I don’t really understand why because this variable is public…

6

Thank you for your time and attention, that’s it! I can continue my tutorial, our explanations are genial !

Have a good day and thank you again!