Hey guys,
first of all, i am sorry for my English.
So i need to say that i am in the beginning of GameDev. I know the basics of c++, and so on, and therefore i wanted to look into Unreal Engine.
My Problem is something like this:
why is it not possible to call, for example, GetOwner() in the Constructor of a component? I thought the Owner is created in the hierachy above the component, and therefore it can refer to the Owner. But why isnt this the case?
Why we need to call GetOwner() in the BeginPlay function?
Is it because the Object or the Instance of the OwnerClass is only then crrated, when i begin to play? So it would be created in the Super::BeginPlay() function?
Is this the same for âGetWorld()â ?
If this is true, is then every object only created after the Super::BeginPlay() function?
I dont know if you guys could understand my question.
Before i wanted to start to learn the Unreal Engine, I programmed some simple stuff in my IDE and i knew what is happening because if i compile and run, the âmainâ function started, if you guys know what i mean. But here i dont really know where is what happening. I know that if i click play, the BeginPlay() function gets called, but where are the objects created and so on?
And again, i am so sorry for my english, i hope that i could express my problem.
You are asking some really fundamental questions about the engine here and answering all of those accurately would take forever. A lot of what you ask can be read-up in the documentation, but I still want to try to make some things clearer for you.
why is it not possible to call, for
example, GetOwner() in the Constructor
of a component?
It is absolutely possible to do that, but you probably mean that often a nullptr is returned from that function in the constructor. A constructor is called whenever an instance of the corresponding class is created. The engine creates and recreates instances of your actor and component classes many times in many different situations, not only when you press BeginPlay. If you place this line of code in the constructor of your classes
FString Name;
GetName(Name);
UE_LOG(LogTemp, Error, TEXT("Ctor called for %s."), *Name)
you will realize just how many instances of your objects the engine constantly creates even outside your game, e.g. during start-up, when you open a Blueprint, when you compile a Blueprint etc. A lot of this has to do with what is called âReflectionâ, which is essentially what allows you to actually see and modify your assets within the editor. The owner of a component may or may not exist when its constructor is called, it depends on the situation. Do not confuse the inheritance hierarchy in C++ with the Entity-Component system of the engine. For C++, yes the base class constructor is always called before the child class constructor, but this has (almost) nothing to do with the Actor-Component hierarchies you create for your game or when ownership gets assigned.
But here i dont really know where is
what happening.
Welcome to the world of software development. Unreal Engine is a huge system and I can assure you that the vast majority of users doesnât know either. The point is, you usually donât need to know. Following the code from main to the point where your actorâs constructor gets called is a very long and tedious road, and you most likely wonât understand a lot either if you donât already have a strong understanding of game engine design. The Unreal interface is really good and especially designed so that you donât need to know these things to make games.
The Unreal framework is kind of specific about what you can/should do in the constructor. Usually you use it to create subobjects and initialize default values. However, there are other functions that get called after the constructor by the engine that make certain guarantees on what is and what is not initialized at that stage. You can override these functions and put your own initialization logic in there. Reference: Actor Lifecycle | Unreal Engine Documentation
If you are content with my answer please mark it as accepted
Thank you so so much! I thought there is a general rule when or where an Instance or Object of a class is created. So i think i should maybe dont use get-functions of classes or other stuff that can be created, in the constructor. Or i should catch the potential errors, nullptr here, if something fails at least, totally forgot about it. Thank you so much for your explanation!!
