Passing a variable to FConstructorStatics

Development Programming & Scripting C++
1

Hi all, I’m trying to create a base class for a bunch of helper actors that can be placed in the editor. These actors will have billboards and static meshes that are not visible in game. I want to be able to put all of the code to initialize these components in the base class, and create new classes that extend from the base class where a simple modification to some default variables define the resource paths for these billboards and meshes. I’m encountering the error **“a nonstatic member reference must be relative to a specific object” **on line 29. I understand that there is a way to pass in arguments, but I’m not sure of the exact syntax.



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

#include "EditorHelperObject.h"

// Sets default values
AEditorHelperObject::AEditorHelperObject(const FObjectInitializer& ObjectInitializer)
    : Super(ObjectInitializer)
{
    // Disable Tick() every frame.
    PrimaryActorTick.bCanEverTick = false;

    SpriteTexturePath = FName(TEXT("/Engine/EditorResources/S_Note"));

    // Structure to hold one-time initialization
    struct FConstructorStatics
    {
        // A helper class object we use to find target UTexture2D object in resource package
        ConstructorHelpers::FObjectFinderOptional<UTexture2D> NoteTextureObject;

        // Icon sprite category name
        FName ID_Notes;

        // Icon sprite display name
        FText NAME_Notes;

        FConstructorStatics()
            // Use helper class object to find the texture
            // "/Engine/EditorResources/S_Note" is resource path
            : NoteTextureObject(SpriteTexturePath)
            , ID_Notes(TEXT("Notes"))
            , NAME_Notes(NSLOCTEXT("SpriteCategory", "Notes", "Notes"))
        {
        }
    };
    static FConstructorStatics ConstructorStatics;

    // We need a scene component to attach Icon sprite
    USceneComponent* SceneComponent = ObjectInitializer.CreateDefaultSubobject<USceneComponent>(this, TEXT("SceneComp"));
    RootComponent = SceneComponent;
    RootComponent->Mobility = EComponentMobility::Static;

#if WITH_EDITORONLY_DATA

    SpriteComponent = ObjectInitializer.CreateEditorOnlyDefaultSubobject<UBillboardComponent>(this, TEXT("Sprite"));
    if (SpriteComponent)
    {

        SpriteComponent->Sprite = ConstructorStatics.NoteTextureObject.Get();                                    // Get the sprite texture from helper class object
        SpriteComponent->SpriteInfo.Category = ConstructorStatics.ID_Notes;                                        // Assign sprite category name
        SpriteComponent->SpriteInfo.DisplayName = ConstructorStatics.NAME_Notes;                                // Assign sprite display name
        SpriteComponent->AttachToComponent(RootComponent, FAttachmentTransformRules::KeepRelativeTransform);    // Attach sprite to scene component
        SpriteComponent->Mobility = EComponentMobility::Static;
        SpriteComponent->bUseInEditorScaling = true;
    }
#endif // WITH_EDITORONLY_DATA
}

// Called when the game starts or when spawned
void AEditorHelperObject::BeginPlay()
{
    Super::BeginPlay();

}

// Called every frame
void AEditorHelperObject::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);

}

I checked out NavigationObjectBase.cpp, and PlayerStart.cpp, which extends from ANavigationObjectBase, and I noticed that both have their own code to create and attach a billboard component. Does all of the constructor code really need to be typed again for child classes?

2

Why do you need FConstructorStatics to be static when you only use it inside constructor?

3

I am trying to learn by looking at existing code, so I’m doing it that way because that’s the only way I’ve seen it done. What would the alternative be?