Binding to the ReceiveMoveCompleted event breaks cooking

Development Programming & Scripting C++
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1

Binding to the AIController’s ReceiveMoveCompleted event in blueprints returns an AIRequestID structure which is not blueprint compatible. Trying to cook the build will fail with the following error.

UATHelper: Packaging (Windows (64-bit)): UnrealBuildTool: C:/GV/Intermediate/Plugins/WindowsNoEditor/NativizedAssets/Source/NativizedAssets/Public/AI_Task_MoveToActor__pf3605976607.h(60) : LogCompile: Error: Type 'FAIRequestID' is not supported by blueprint. bpf__cb_ReceiveMoveCompleted__pf.bpp__RequestID__pf
2

As a workaround, in C++ you can fire a replacement delegate in a child class for AIController, but obviously that won’t help for blueprint-only projects.

(See code below for details!)

3

Any chance you could explain this more in depth please? I’m getting the same answer and don’t understand how to implement your workaround.

4

Sure thing - here’s the code from my project for a new child class of AAIController:

#pragma once

#include "CoreMinimal.h"
#include "AIController.h"
#include "GV_CPP_AIController.generated.h"


DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FGV_AIC_MoveCompleted, EPathFollowingResult::Type, Result);

/**
 * 
 */
UCLASS()
class GONEVIRAL_API AGV_CPP_AIController : public AAIController
{
	GENERATED_BODY()


	UPROPERTY(BlueprintAssignable, BlueprintCallable)
		FGV_AIC_MoveCompleted Callback_AIController_MoveCompleted;

	// Overriding base 
	void OnMoveCompleted(FAIRequestID RequestID, const FPathFollowingResult& Result) { Super::OnMoveCompleted(RequestID, Result);  Callback_AIController_MoveCompleted.Broadcast(Result.Code); };
};

All we’re doing there is extending the function OnMoveCompleted, and throwing a new delegate we’ve made called Callback_AIController_MoveCompleted.

We can use that new delegate no problem in blueprints, because it is marked as BlueprintAssignable and BlueprintCallable and avoids passing along the FAIRequestID - which fixes the issue when building.

I’ll make my original answer more clear if it’ll still let me edit it :slight_smile:

5

In our project we’re essentially using only blueprints (minus a few custom procedural things done in C++). In order to do this for our BP_AIC, is there any way to create a child of a blueprint as C++?
I know that’s a longshot but figured I’d ask.

Thanks for such a quick response! Glorious!

6

No problem!

Unfortunately I don’t think there’s a blueprint only workaround, because the issue at heart is that the engine is using a type in its delegate that blueprints don’t understand (FAI_RequestID) and when nativizing that issue is causing the error you see.

The deep bug here is that apparently UE is OK with that non-blueprint struct appearing in blueprints via a function signature in the editor but not in natvizing/packaging.

Without fixing that probably-tricky bug, the easy engine fix would be to make that struct blueprintable (basically adding a single keyword to the declaration of the struct) but you’d need to be patching in that one-word, presumably trivial, engine fix for that.

If you know someone friendly who submits engine bugfixes they could well help with that bit.

One other thought - if you set your particular blueprint that references this to not be nativized does that avoid this?

7

Oh, and to answer your question when I read more closely - you can’t have a C++ class parented to a blueprint class. But you can make a very similar class to the one I made (basically replacing GONEVIRAL_API with your project API, and naming it without the GV we use for classes) in C++ and then reparent your existing AI controller-child blueprint (BP_AIC) to that new class.