How do i properly Add Elements to the TArray

Development Programming & Scripting C++
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1

I am trying to create a TArray Recoil Pattern for my Gun with 30 different FVector coordinates for each bullet. I went through tultorial videos and read Array Containers in Unreal Engine | Unreal Engine Documentation this guide for adding to the array.I tried using Add, Emplace, Innit to no avail. I even set the size to 30 with SetNum, still didn’t work i do not understand what my issue is with adding elements to the TArray. I keep getting this crash error :

Screenshot (563)
Screenshot (563)955×563 13.3 KB

this is my GunProperties.H:

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "Components/BoxComponent.h"
#include "Camera/CameraComponent.h"
#include "GunProperties.generated.h"


#define TRACE_WEAPON  ECC_GameTraceChannel1
UENUM(BlueprintType)
namespace EWeaponProjectile
{
    enum ProjectileType
    {
        EBullet     UMETA(DisplayName = "Bullet"),
        ESpread     UMETA(DisplayName = "Spread"),
        EProjectile UMETA(DisplayName = "Projectile"),
    };
}



USTRUCT()
struct FWeaponData
{
    GENERATED_USTRUCT_BODY()

    
    UPROPERTY(EditDefaultsOnly, Category = Ammo)
        int32 MaxAmmo;
    UPROPERTY(EditDefaultsOnly, Category = Config)
        float TimeBetweenShots;
    UPROPERTY(EditDefaultsOnly, Category = Ammo)
        int32 ShotCost;
    UPROPERTY(EditDefaultsOnly, Category = Config)
        float WeaponRange;
    UPROPERTY(EditDefaultsOnly, Category = Config)
        float WeaponSpread;
    UPROPERTY(EditDefaultsOnly, Category = Config)
        float recoilResetTimeSeconds;
    UPROPERTY(EditDefaultsOnly, Category = Config)
        float lastTimeShotForAr;

};
UCLASS()
class PLAYERVSAI_API AGunProperties : public AActor
{
    GENERATED_BODY()



    
public: 
    
    // Called when the game starts or when spawned
    AGunProperties();
    // Called every frame
    UFUNCTION()
    void Fire(const FVector CameraDir);
    
    UFUNCTION()
    void InstantFire(const FVector CameraDir);

    virtual void BeginPlay() override;

    UPROPERTY(EditDefaultsOnly, Category = Config)
    FWeaponData WeaponConfig;

    UPROPERTY(EditDefaultsOnly, BlueprintReadWrite, Category = Config)
    TEnumAsByte<EWeaponProjectile::ProjectileType> ProjectileType;

    UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = Collision)
        UBoxComponent* CollisionComp;

    UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = Config)
        USkeletalMeshComponent* WeaponMesh;

    /*void InterpAiming(float DeltaSeconds);
    void InterpRelativeHand(float DeltaSeconds);*/
    
    FTransform RecoilTransform;

    FTransform FinalRecoilTransform;
    
    
    //Handle Vector Recoil , returns New Location
    protected:

        FHitResult WeaponTrace(const FVector &TraceFrom, const FVector &TraceTo) const;

        void HandleARShooting(UCameraComponent* Camera);

        void ProcessInstantHit(const FHitResult& Impact, const FVector& Origin, const FVector& ShootDir, int32 RandomSeed, float RadicalSpread);

        void ProcessInstantHitForAR(const FHitResult& Impact, const FVector& Origin);
        
        TArray<FVector> RecoilPattern[];
        
    
};```

This is my GunProperties.cpp: 

#include "GunProperties.h"

#include "Engine.h"

AGunProperties::AGunProperties() 
{
    PrimaryActorTick.bCanEverTick = false;
    CollisionComp = CreateDefaultSubobject<UBoxComponent>(TEXT("CollisionComp"));
    RootComponent = CollisionComp;

    WeaponMesh = CreateDefaultSubobject<USkeletalMeshComponent>(TEXT("Gun Mesh"));
    WeaponMesh->AttachTo(RootComponent);
    
    
    
}

void AGunProperties::BeginPlay()
{
    Super::BeginPlay();
    if (ProjectileType == EWeaponProjectile::EBullet)
    {
        RecoilPattern->SetNum(30);

        RecoilPattern->Emplace(FVector(-0.2, 0, 0));
        RecoilPattern->Emplace(FVector(-0.2, 0, 0));
        RecoilPattern->Emplace(FVector(-0.2, 0, 0));
        RecoilPattern->Emplace(FVector(-0.2, 0, 0));
        RecoilPattern->Emplace(FVector(-0.2, 0, 0));
        RecoilPattern->Emplace(FVector(-0.2, 0, 0));

        RecoilPattern->Emplace(FVector(-0.3, 0, 0));
        RecoilPattern->Emplace(FVector(-0.3, 0, 0));
        RecoilPattern->Emplace(FVector(-0.3, 0, 0));
        RecoilPattern->Emplace(FVector(-0.3, 0, 0));
        RecoilPattern->Emplace(FVector(-0.3, 0, 0));
        RecoilPattern->Emplace(FVector(-0.3, 0, 0));

        RecoilPattern->Emplace(FVector(-0.5, 0, 0));
        RecoilPattern->Emplace(FVector(-0.5, 0, 0));
        RecoilPattern->Emplace(FVector(-0.5, 0, 0));
        RecoilPattern->Emplace(FVector(-0.5, 0, 0));
        RecoilPattern->Emplace(FVector(-0.5, 0, 0));
        RecoilPattern->Emplace(FVector(-0.5, 0, 0));

        RecoilPattern->Emplace(FVector(0, -0.3, 0));
        RecoilPattern->Emplace(FVector(0, -0.3, 0));
        RecoilPattern->Emplace(FVector(0, -0.3, 0));
        RecoilPattern->Emplace(FVector(0, -0.3, 0));
        RecoilPattern->Emplace(FVector(0, -0.3, 0));
        RecoilPattern->Emplace(FVector(0, -0.3, 0));

        RecoilPattern->Emplace(FVector(0, 0.3, 0));
        RecoilPattern->Emplace(FVector(0, 0.3, 0));
        RecoilPattern->Emplace(FVector(0, 0.3, 0));
        RecoilPattern->Emplace(FVector(0, 0.3, 0));
        RecoilPattern->Emplace(FVector(0, 0.3, 0));
        RecoilPattern->Emplace(FVector(0, 0.3, 0));
    }
}
void AGunProperties::Fire( FVector CameraDir)
{
    if (ProjectileType == EWeaponProjectile::EBullet)
    {
        GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Black, TEXT("Bullet"));
        
        

        
        //InstantFire(CameraDir);
    }
    if (ProjectileType == EWeaponProjectile::ESpread)
    {
        GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Black, TEXT("Spread"));
        for (int32 i = 0; i <= WeaponConfig.WeaponSpread; i++)
        {
            InstantFire(CameraDir);
        }
    }
    if (ProjectileType == EWeaponProjectile::EProjectile)
    {
        GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Black, TEXT("Projectile"));
    }
}

 void AGunProperties::InstantFire( FVector CameraDir)
{
    const int32 RandomSeed = FMath::Rand();
    FRandomStream WeaponRandomStream(RandomSeed);
    const float CurrentSpread = WeaponConfig.WeaponSpread;
    const float SpreadCone = FMath::DegreesToRadians(WeaponConfig.WeaponSpread );
    const FVector StartTrace = WeaponMesh->GetSocketLocation("MF");
    const FVector ShootDir = WeaponRandomStream.VRandCone(StartTrace, SpreadCone, SpreadCone);
    const FVector EndTrace = StartTrace + ShootDir * WeaponConfig.WeaponRange;
    const FHitResult Impact = WeaponTrace(StartTrace, EndTrace);

    ProcessInstantHit(Impact, StartTrace, ShootDir, RandomSeed, CurrentSpread);
}



FHitResult AGunProperties::WeaponTrace(const FVector& TraceFrom, const FVector& TraceTo) const
{
    static FName WeaponFireTag = FName(TEXT("WeaponTrace"));
    FCollisionQueryParams TraceParams(WeaponFireTag, true);
    TraceParams.bReturnPhysicalMaterial = true;
    TraceParams.AddIgnoredActor(this);

    FHitResult Hit(ForceInit);
    GetWorld()->LineTraceSingleByChannel(Hit, TraceFrom, TraceTo, TRACE_WEAPON, TraceParams);
    return Hit;
}

void AGunProperties::HandleARShooting(UCameraComponent* Camera)
{
    if (GetWorld()->DeltaTimeSeconds - WeaponConfig.lastTimeShotForAr / WeaponConfig.TimeBetweenShots)
    {
        //We shoot
        const FVector StartTrace = WeaponMesh->GetSocketLocation("MF");
        const FVector ShootDir = FVector(StartTrace);
        const FVector EndTrace = StartTrace * WeaponConfig.WeaponRange;
        const FHitResult Impact = WeaponTrace(StartTrace, EndTrace);
        ProcessInstantHitForAR(Impact, StartTrace);
        WeaponConfig.lastTimeShotForAr = GetWorld()->DeltaTimeSeconds;
    }
}



void AGunProperties::ProcessInstantHit(const FHitResult& Impact, const FVector& Origin, const FVector& ShootDir, int32 RandomSeed, float RadicalSpread)
{
    const FVector EndTrace = Origin + ShootDir * WeaponConfig.WeaponRange;
    const FVector EndPoint = Impact.GetActor() ? Impact.ImpactPoint : EndTrace;
    DrawDebugLine(this->GetWorld(), Origin, Impact.TraceEnd, FColor::Black,false, 1000, 10.f);
}

void AGunProperties::ProcessInstantHitForAR(const FHitResult& Impact, const FVector& Origin)
{
    const FVector EndTrace = Origin* WeaponConfig.WeaponRange;
    const FVector EndPoint = Impact.GetActor() ? Impact.ImpactPoint : EndTrace;
    DrawDebugLine(this->GetWorld(), Origin, Impact.TraceEnd, FColor::Black, false, 1000, 10.f);
}
2

You don’t need square brackets when you declare the array. It results in an error. Just TArray<FVector> RecoilPattern;

Or you can define the elements right away, if they don’t change:
TArray<FVector> RecoilPattern {FVector(-0.2, 0, 0), FVector(-0.2, 0, 0), ... };

And I believe SetNum(30) and then Emplace() will make your array longer with a lot of empty values (or in this case with elements 0-29 being FVector(0,0,0); If you don’t want to define the values in the .h file, you can simply .Add() elements on BeginPlay();

3

You’re calling Array.SetNum(30); which will create 30 default-constructed items, then following it up with calls to Emplace which will construct new items after that original 30.

If you want to pre-allocate space to add items (which you should if you know the amount), use Array.Reserve(30);

Add and Emplace are similar but not the same. Add will invoke a copy, whereas Emplace will construct the item in the array and avoid a copy. Where possible, prefer to use Emplace over Add (it matters less for trivial types, like pointers, floats etc.)

4

Thank you for explaining the SetSum and Reserve() , i thought SetSum was something like SetSize of the array .

5

hmm , i guess my C++ knowledge is bad , i though you declare variables for Classes in specific places , i.e. Construct , int main() , Void::BeginPlay, Void::Update , mostly functions and Constructors and not in the header file. Guess i still haven’t wraped my head around properly about C++ and Object Oriented Programming. Thank you for the advice. I will give it a try.