Building Escape crashes after following Physics Handles lecture(Lecture no 125)

[mogamb_o]

Hi, my unreal engine is crashing after following the lecture physics handle in the building escape game.

Here’s the crash error:

I think that the main cause of the problem is as follows:

Because whenever I comment out these lines marked in red rectangle my engine doesn’t crash.

Here’s “GrabbeClass.cpp” code file:

// Developer: Muneeb Muzammal(H00387067)

#include "GrabberClass.h"	
#include "DrawDebugHelpers.h" //Headerfile to draw a line from player
#include "Engine/World.h"
#include "GameFramework/PlayerController.h" //Headerfile to control player's view point


#define OUT
// Sets default values for this component's properties
UGrabberClass::UGrabberClass()
{
	// 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;
}


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

	FindPhysicsHandle();
	InputComponentSetup();

	
	
}

void UGrabberClass::InputComponentSetup() 
{
	inputComponent = GetOwner()->FindComponentByClass<UInputComponent>();
	if (inputComponent)
	{
		inputComponent->BindAction("Grab", IE_Pressed, this, &UGrabberClass::Grab); //When press the grab key set out in engine this will refer to grab function
		inputComponent->BindAction("Grab", IE_Released, this, &UGrabberClass::Release);
	}
}

	//Check for physics handle component
void UGrabberClass::FindPhysicsHandle()
{
	physicsHandle = GetOwner()->FindComponentByClass<UPhysicsHandleComponent>(); //Because Getowner is common in physicsHandle and in grabber
	
	if (physicsHandle)
	{
	}
	else
	{
		UE_LOG(LogTemp, Error, TEXT("No physics handle component find on %s!"), *GetOwner()->GetName());
	}
}
void UGrabberClass::Grab()
{
	UE_LOG(LogTemp, Warning, TEXT("Grabber pressed!"));

	
	FVector playerViewPointLocation;
	FRotator playerViewPointRotation;
	GetWorld()->GetFirstPlayerController()->GetPlayerViewPoint(
		OUT playerViewPointLocation,
		OUT playerViewPointRotation
	);

	FVector LineTraceEnd = playerViewPointLocation + playerViewPointRotation.Vector() * playerReach;

	FHitResult HitResult = GetFirstPhysicsBodyInReach();
	UPrimitiveComponent* ComponentToGrab = HitResult.GetComponent(); //UPrimitive Component
	// Attach the physics handel if we hit something
	if (HitResult.GetActor())
	{
		//TODO attach physics handle
		physicsHandle->GrabComponentAtLocation
		(
			ComponentToGrab,
			NAME_None,
			LineTraceEnd
		);
	}
}

void UGrabberClass::Release()
{
	UE_LOG(LogTemp, Warning, TEXT("Grabber released!"));
	
	//TODO Release physics handle

}

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

	// Get Player's view point
	FVector playerViewPointLocation; 
	FRotator playerViewPointRotation;
	GetWorld()->GetFirstPlayerController()->GetPlayerViewPoint(
		OUT playerViewPointLocation,
		OUT playerViewPointRotation
	);

	FVector LineTraceEnd = playerViewPointLocation + playerViewPointRotation.Vector() * playerReach;

	//If physics handle is attached 
	if (physicsHandle->GrabbedComponent)
	{
		//Move abject we are holding
		physicsHandle->SetTargetLocation(LineTraceEnd);
		
	}
}

FHitResult UGrabberClass::GetFirstPhysicsBodyInReach() const
{

	// Get Player's view point
	FVector playerViewPointLocation;
	FRotator playerViewPointRotation;
	GetWorld()->GetFirstPlayerController()->GetPlayerViewPoint(
		OUT playerViewPointLocation,
		OUT playerViewPointRotation
	);

	FVector LineTraceEnd = playerViewPointLocation + playerViewPointRotation.Vector() * playerReach;

	FHitResult Hit;
	// Ray-cast out to a certain distance (Reach)

	FCollisionQueryParams TraceParams(FName(TEXT("")), false, GetOwner());

	GetWorld()->LineTraceSingleByObjectType(
		OUT Hit,
		playerViewPointLocation,
		LineTraceEnd,
		FCollisionObjectQueryParams(ECollisionChannel::ECC_PhysicsBody),
		TraceParams
	);

	AActor* actorHit = Hit.GetActor();

	if (actorHit)
	{
		UE_LOG(LogTemp, Warning, TEXT("LineTrace is hit: %s"), *(actorHit->GetName()))
	}

	return Hit;
}

And here’s “GrabberClass.h” code file:

// Developer: Muneeb Muzammal(H00387067)

#pragma once

#include "CoreMinimal.h"
#include "Components/ActorComponent.h"
#include "PhysicsEngine/PhysicsHandleComponent.h"
#include "GrabberClass.generated.h" 


UCLASS(ClassGroup = (Custom), meta = (BlueprintSpawnableComponent))
class ESCAPE_API UGrabberClass : public UActorComponent
{
	GENERATED_BODY()

public:
	// Sets default values for this component's properties
	UGrabberClass();


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


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


private:

	float playerReach = 100.0f;

	UPhysicsHandleComponent* physicsHandle = nullptr;
	UInputComponent* inputComponent = nullptr;

	void Grab();
	void Release();
	void FindPhysicsHandle();
	void InputComponentSetup();

	//Return the first actor within reach with physics body
	FHitResult GetFirstPhysicsBodyInReach() const;

};

Thank you.

[telesphorosgames]

add a check for physics handle as well , make your if check look like this :

if ( physicsHandle && physicsHandle->GrabbedComponent)

It’s best practice to always check EVERY pointer to make sure they are valid before using them.

cheers!
Tele

[mogamb_o]

Thank you very much, It worked. Stay Blessed!