Blueprint Nativization turns TSubclassOf into UClass* which prevents build

Development Programming & Scripting Blueprint
, , , , , ,
1

Hello,

After a customer reported a problem with packaging my plugin using Blueprint Nativization I tracked down a bug. I use a couple of BlueprintNativeEvent UFUNCTIONs, but the generated nativization code contains errors. I picked an example method in one of my classes. This is how it is declared:

UFUNCTION(BlueprintCallable, BlueprintNativeEvent, Category = "AdvKit")
bool CreateTransitionBetween(TSubclassOf<AAdvKitCharacter> ForCharacterClass, AAdvKitZone* SourceZone, AAdvKitZone* TargetZone);
virtual bool CreateTransitionBetween_Implementation(TSubclassOf<AAdvKitCharacter> ForCharacterClass, AAdvKitZone* SourceZone, AAdvKitZone* TargetZone);

The signature inside the generated blueprint c++ code looks like this however:

virtual void CreateTransitionsFor_Implementation(UClass* bpp__ForCharacterClass__pf, AAdvKitZone* bpp__ForZone__pf) override;

The first argument’s type has been changed from TSubclassOf to UClass* resulting in the compiler throwing this error:

UATHelper: Packaging (Windows
(64-bit)): UnrealBuildTool:
C:\Project\Intermediate\WindowsNoEditor\NativizedAssets\Source\NativizedAssets\Public/BP_LadderStepBuilder__pf964772836.h(20): error C3668:
‘UBP_LadderStepBuilder_C__pf964772836::CreateTransitionsFor_Implementation’:
method with override specifier
‘override’ did not override any base
class methods

This happens for every method using TSubclassOf as an argument. I hotfixed it by introducing a virtual method in the base class that matches the signature and calls the correct method:

bool UAdvKitTransitionBuilderModule::CreateTransitionBetween_Implementation(UClass* ForCharacterClass, AAdvKitZone* SourceZone, AAdvKitZone* TargetZone)
{
	if (!ForCharacterClass->IsChildOf(AAdvKitCharacter::StaticClass()))
	{
		return false;
	}

	TSubclassOf<AAdvKitCharacter> Class = ForCharacterClass;
	return CreateTransitionBetween_Implementation(Class, SourceZone, TargetZone);
}

However that is no permanent fix and it also adds unecessary overhead to every method. I don’t want to change my code to use UClass* because if a TSubclassOf is exposed in Blueprint the editor automatically filters the class list to show only applicable ones.

Kind Regards,

2

Can confirm, i’m experiencing exact same bug:

3

Hi ,

This does appear to be the same issue that was reported by moookiexl in the linked post. I have added some additional information to UE-42676 to reflect your report.

4

I’m sorry to inform you that even if the tickes is signed as Fixed for 4.16,
on 4.16.2 i’m still having this issue

5

And i’ll add in another issue:

UFUNCTION(BlueprintCallable, BlueprintNativeEvent, Category = "ImperoResources")
	bool CanBeFarmedBy(const TScriptInterface<IEntityInterface>& Entity) const;
	bool CanBeFarmedBy_Implementation(const TScriptInterface<IEntityInterface>& Entity) const { return true; };

(as you can see, a input parameter)

gets nativized as:

virtual bool  CanBeFarmedBy_Implementation(/*out*/ TScriptInterface<IEntityInterface> const& bpp__Entity__pf__const) const override;

So an out parameter, giving an error.

6

The bug has been fixed in 4.17 ( Unreal Engine Issues and Bug Tracker (UE-44511) )

7

Hi zamy,

Sorry for not responding sooner. I am no longer able to reproduce the issue that was reported in UE-42676. Are you still running into it? If so, would you be able to provide a small test project where the issue is still occurring?