How I can attach an actor to a box component?

Development Programming & Scripting
1

Hello,

I have created a graph (derived from AActor) class where I want to store all of the graph nodes. The graph has a box component where every node should be attached to. In addition to that I have created a node class which is also derived from AActor. Now I want to spawn the nodes corresponding to the boxcomponent width and depth and saving them in an array inside the graph class. But where/how could I actually attach those actors to my box component ?

2

https://docs.unrealengine.com/latest/INT/API/Runtime/Engine/GameFramework/AActor/AttachRootComponentToActor/index.html

3

You might also try using UChildActorComponent, which allows you to attach actor as a component to other actor. It can be used more like a slots

4

Okay, well I have corrected my question. I forgot about the fact I am actually want to attach the node to the box component. My fault. But I have tried it with AttachRootComponentTo, everything compiles correctly but the editor is crashing. I am using this code:

ANode* tempNode = CreateAbstractDefaultSubobject<ANode>(TEXT("Node"));

	tempNode->AttachRootComponentTo(this->nodeContainer, NAME_None, EAttachLocation::SnapToTarget);

where the type of nodeContainer is UBoxComponent

5

I believe abstract default subobjects are null in the constructor until you actually provide a class in a subclass. So the pointer returned from that function is null. Then you’re dereferencing a null pointer. maybe

That or your nodeContainer pointer is null.

6

Okay so I have also tried your method but it also crashed my editor :frowning: My code I was using :
FVector boxSize = this->nodeContainer->GetScaledBoxExtent();
UChildActorComponent* tempNodeKeaper = CreateAbstractDefaultSubobject(TEXT(“nodeKeaper”));
ANode* tempNode = CreateAbstractDefaultSubobject(TEXT(“node”));

	tempNodeKeaper->AttachTo(this->nodeContainer);

	tempNode->nodeMesh= this->nodeMesh;

	tempNodeKeaper->ChildActor = tempNode;
7

If I understand it correctly why don’t you create some “node holders” on your box component and spawn your nodes giving them the location/rotation of those holders you have?, like having sockets on a mesh and attaching something to it?

Also AttachRootComponentTo I believe it only works for skeletal meshes, so in this case you just have to either find a way to create a socket on the box component (I have no clue whether this is possible) or set the location of the nodes on the box.

Hope this helps ^^

8

I have set a breakpoint for checking if one of them is null. And everyone seems to be initialized correctly.

9

But I have tried it with blueprints and it seems to work, now I only have to figure out what coding mistake I have made :slight_smile: Update when It has succeeded

10

Good idea in theorie but I couldnt figure it out how to create a socket on a BoxComponent

11

Then no idea. :frowning:

12

Try debugging and see the logs, therem ight be info in log

13

Cast of Graph /Script/MyProject2.Default__Graph to Level failed this is the only showed error I have also commented out everything except this line: ANode* tempNode = CreateAbstractDefaultSubobject(TEXT("node")); so my node class creates this error. Mh and when I set a breakpoint it seems to inintialized correctly: tempNode = 0x000001da58d61000 {neighbours={AllocatorInstance={Data=0x0000000000000000 } ArrayNum=0 ArrayMax=...} ...}.

14

It’s probably because you’re trying to create an actor as a default subobject. That doesn’t work. Use a child actor component.

15

yea subclass might be a issue, spawn object on BeginPlay insted of constructor

16

I have found the setChildActorComponent(TSubClassOf(AActor)) method on the UChildActorComponent. But I cant really find how I could use setChildActorComponent(new ANode()); is wrong

17

You can’t use new on UObjects, for actors use

()->SpawnActor<ANode>()

But do it on BeginPlay this wont work in constructor, you will have crash

18

If I use `

ANode* tempNode =
()->SpawnActor()

it breaks intoUE_CLOG(!CurrentInitializer, LogObj, Fatal, TEXT(“No object initializer found during construction.”)`

PS.: SpawnActorLESSTHANANodeGREATERTHAN()

19

I believe this is not the way to go since I don’t think it’s possible, I’m no expert but I’d create an empty holder for the nodes to be “attached” to.

20

You cannot spawn actors in the constructor or use actors as default sub components.