FWorldDelegates_Example.cpp

// non static
FDelegateHandle handle = FWorldDelegates::OnCurrentLevelChanged.AddUObject(this, &Foo::OnLevelLoaded);

// static
FWorldDelegates::FWorldInitializationEvent::FDelegate Foo::OnPostWorldInitHandle = nullptr;

Foo::Bar()
{
	if (!OnPostWorldInitHandle.IsBound())
	{
		OnPostWorldInitHandle = FWorldDelegates::FWorldInitializationEvent::FDelegate::CreateStatic(&Foo::OnWorldInit);
		FWorldDelegates::OnPostWorldInitialization.Add(OnPostWorldInitHandle);
	}
}

void Foo::OnWorldInit(UWorld* World, const UWorld::InitializationValues IVS)
{
	GEngine->AddOnScreenDebugMessage(-1, 5.5f, FColor::Blue, TEXT("OnWorldInit!"));
	FLatentActionInfo Info;
 	UGameplayStatics::LoadStreamLevelBySoftObjectPtr(World, LoadingDrill->DrillSublevel, true, false, Info);
}

FWorldDelegates_Example.h

// non-static
UFUNCTION()
void OnLevelLoaded(ULevel* NewLevel, ULevel* OldLevel, UWorld* World);


// static
static void OnWorldInit(UWorld* World, const UWorld::InitializationValues IVS);
static FWorldDelegates::FWorldInitializationEvent::FDelegate OnPostWorldInitHandle;