UObject self destruct

Development Programming & Scripting C++
1

Hello everyone! I try create UObject class which will self destroyed in a period of time.
Here code which I made:
.h


#pragma once
#include "TestObject.h"
#include "TO_1.generated.h"
UCLASS()
class TESTCODE_API UTO_1 : public UTestObject
{
	GENERATED_BODY()
	
	virtual void DoThing(FVector SpawnLocation, FRotator SpawnRotation, AActor* Owner, APawn* Iniciator, TSubclassOf<class ATestCodeProjectile> ProjectileClass) override;
private:
	FTimerHandle TimerToDestroy;
	void DestroyFunction();
};

.cpp


#include "TestCode.h"
#include "Engine.h"
#include "TestCodeProjectile.h"
#include "TO_1.h"

void UTO_1::DoThing(FVector SpawnLocation, FRotator SpawnRotation, AActor* Owner, APawn* Iniciator, TSubclassOf<class ATestCodeProjectile> ProjectileClass)
{
	World = Owner->GetWorld();
	if (World != NULL)
	{
		FActorSpawnParameters SpawnParams;
		SpawnParams.Owner = Owner;
		SpawnParams.Instigator = Iniciator;
		World->SpawnActor<ATestCodeProjectile>(ProjectileClass, SpawnLocation, SpawnRotation, SpawnParams);
		GEngine->AddOnScreenDebugMessage(-1, 2.f, FColor::Red, FString::Printf(TEXT("Projectail Spawned (from TO_1)")));
		World->GetTimerManager().SetTimer(TimerToDestroy, this, &UTO_1::DestroyFunction, 3.f, false, 3.f);
	}
}

void UTO_1::DestroyFunction()
{
	GEngine->AddOnScreenDebugMessage(-1, 2.f, FColor::Green, FString::Printf(TEXT("Destroy Object (from TO_1)")));
}

This is all working. When I created this object and call function “DoThing” it spawned projectile and run timer which will fire “DestroyFunction” in 3 sec. As I say, it is all working perfectly. But when I try destroy object itself through “DestroyFunction” like this


void UTO_1::DestroyFunction()
{
	GEngine->AddOnScreenDebugMessage(-1, 2.f, FColor::Green, FString::Printf(TEXT("Destroy Object (from TO_1)")));
	this->ConditionalBeginDestroy();
	this->FinishDestroy();
}

it crashes. So, why it so, and how actually I can selfdestroy UObject?

2

what is the error message and at what line?

3

There is no error. Engine just crushes when I tried fire “DestroyFunction”

Screen.PNG
Screen.PNG839×762 74.7 KB

4

Replace FinishDestroy(); with ConditionalFinishDestroy();

5

I try this, but object do not dispose of.

6

AFAIK, you’re not usually supposed to manually destroy UObjects: they are meant to be automatically cleaned by the garbage collector when there are no more references to them. If you want to kill an object without going through all of its references, call MarkPendingKill() on it so the garbage collection will dispose of it the next time it runs. After calling MarkPendingKill() functions like IsValid(Obj) will return false, so references to that object will be unusable even if the GC hasn’t run yet.

7

Many thanks! That is what I searched.

8

couple things
1 . if you are running in debug mode “f5” you will see the line and exception thrown in VS
2 . Manoelneto is correct! Why do you need to manually destroy it? what ever references the UObject should really be nullifying it (UObjectRef = nullptr) then the GC will deal with it.