How to prevent projectile object from being garbage collected.

Development Programming & Scripting C++
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1

Hi, i’m new to Unreal and trying to figure out why my projectile is being garbage collected.

I allocate it in the constructor of my character using

ProjectileClass = CreateDefaultSubobject<AProjectile>(L"Projectile");

The Character object I am using it in still exists and is valid. Eventually after a random period of time just the projectile becomes invalid and gets sent through the garbage collector. I can find that it was invalid and solve it by using

if (!ProjectileClass->IsValidLowLevel())
{
	ProjectileClass = NewObject<AProjectile>();
}

Which solves all the crashes. But I am curious how to prevent it from being garbage collected when it’s being used in the first place.

2

It needs to be in a UPROPERTY in the header file to not be garbage collected.

UPROPERTY()
  UObject* YourObject;

garbage-collection-dynamic-memory-allocation

garbage_collection_of_variables

garbage-collection-in-unreal-engine

3

Is it declared a UPROPERTY ?

4

AProjectile is an actor class, use SpawnActor instead of NewObject.

5

You are right. That also makes my comment about the UPROPERTY invalid in this case, because the level automatically references spawned actors.
Also, isn’t “CreateDefaultSubobject” only valid for ActorComponents?

6

Well kind of. AActors and UActorComponents are both UObjects, and garbage collection happens at the UObject level. CreateDefaultSubobject is a function of UObject and can be used with any UObject (not just components). I believe it establishes a subobject relationship in the constructor (that works with the CDO system). So if you have a UObject-derived UPROPERTY in a class you can call CreateDefaultSubobject in the constructor to populate it (in the CDO). I’m not entirely clear what the difference is between CreateDefaultSubobject and using NewObject in the constructor. I also could be wrong about everything I just said.