Exposing function to blueprints?

Development Programming & Scripting C++
1

I’m doing the quickstart on the official documentation and I’m having trouble exposing my CalculateValues function to blueprints. It looks pretty simple:

[MyActor.h]



UFUNCTION(BlueprintCallable, Category = "Damage")
void CalculateValues();

After building I cannot find the CalculateFunction or the Damage category inside the blueprints. The function is public, but my guess is it would not compile when it is anything other then public. What am I missing?

2

My guess is that this is a hot reload issue. You can find a detailed explanation of the issue here, but the short version is that UPROPERTY()s and UFUNCTION()s are not always properly updated after a hot reload. Thankfully, the work around is simple - close and reopen the editor and everything should be in the right place.

3

I can confirm that with 4.7.2 (windows7 x64, visualstudio2013) this issue is raised against the official documentation (Programming with C++ in Unreal Engine | Unreal Engine 5.2 Documentation)

Closing and opening again the editor fix the issue. I just wonder if this issue is related just to this particular version (4.7.2).

4

This is working as expected in 4.7.2.

Have you also implemented the function in MyActor.cpp?

5

yeppa i have!

6

Could you post your MyActor.h and .cpp file?

7

I’ve notice that if i change the Category (from DAMAGE to DAMAGETWO) in visualstudio (and rebuild the project) the HOTRELOAD in blueprint recognize something happen, but pressing the right button, the new category (DAMAGETWO) is still not available (as pointed out by Madmenyo). If i restart the editor, the DAMAGETWO is available

Am I missing something?



// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "GameFramework/Actor.h"
#include "MyActor.generated.h"

UCLASS()
class MYPROJECT_API AMyActor : public AActor
{
	GENERATED_BODY()
	
public:	

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Damage")
		int32 TotalDamage;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Damage")
		float DamageTimeInSeconds;

	UPROPERTY(BlueprintReadOnly, VisibleAnywhere, Transient, Category = "Damage")
		float DamagePerSecond;


	// Sets default values for this actor's properties
	AMyActor();

	// Called when the game starts or when spawned
	virtual void BeginPlay() override;

	virtual void PostInitProperties() override;

	void  PostEditChangeProperty(FPropertyChangedEvent& PropertyChangedEvent) override;

	UFUNCTION(BlueprintCallable, Category = "Damage")
		void CalculateValues();
};




// Fill out your copyright notice in the Description page of Project Settings.

#include "MyProject.h"
#include "MyActor.h"

// Sets default values
AMyActor::AMyActor()
{
	TotalDamage = 200;
	DamageTimeInSeconds = 1.f;
}

// Called when the game starts or when spawned
void AMyActor::BeginPlay()
{
	Super::BeginPlay();
}

void AMyActor::PostInitProperties()
{
	Super::PostInitProperties();
	
	CalculateValues();
}

void AMyActor::CalculateValues()
{
	DamagePerSecond = TotalDamage / DamageTimeInSeconds;
}

#if WITH_EDITOR
void AMyActor::PostEditChangeProperty(FPropertyChangedEvent& PropertyChangedEvent)
{
	CalculateValues();

	Super::PostEditChangeProperty(PropertyChangedEvent);
}
#endif
8

I had no problems to compile the code from within the editor and from visual studio.

The Calculate Value function shows up as expected.

I would recommend to create a new project. Maybe you broke some other part.

9

My rule of thumb is that if you change something in the header file, you can’t use hot reload. Just rebuild the project in visual studio. If you only change code in the CPP files, then the hot reload works great.

If you’re doing a build from VS and still not seeing the function in your blueprint, then there’s something else going on. It looks correct in your posted code though.

10

Did you make sure to untick that context option in BP? I had the same problem as you, but when I de-selected it I found my function in the set category.

11

That used to be the case, but these days (in 4.7) you should be able to change headers as well and it should all work! If it doesn’t that is probably a bug, and AnswerHub is the best place to post those.

12

I don’t trust hot reloads 100% because they still cause problems for me if I change a lot. For instance if I add a new BlueprintCallable function, then hot reload my changes, add the function to a BP then attempt to save that BP, I get an error telling me the BP couldn’t be saved due to an external reference. If I however, add the function then recompile from Visual Studio, no problems.

13

Well I also happen to be following the same introductory tutorial and I am having the same issue as well with the UFUNCTION macro too… gonna try restarting my editor and see what happens.

15

Yea so after restarting the editor and turning off context sensitive the function shows up as well as its respective category. So this appears to be a bug of some sort as I had also tried building from Visual Studio and it does not show up either.

17

like others pointed out on this thread, seems to me that some issues related with hot reload are still there.

i’ve opened a ticket here