UFunction return TArray

Development Programming & Scripting C++
, , , ,
1

Hey,

so I am fairly new to C++ coding in general, not just when it comes to Unreal. I have some good knowledge in C#, Java and other languages however C++ is a different level to me.

I am trying to return a TArray from a void (UFunction) into BluePrint but I can not get it to work. I saw you can do it without using “return” but by putting it into the void parameters. That has worked but not with TArray for some reason and I don’t really understand why it’s not working.

Could anyone explain how it has to be done and show an up-to-date example that is actually working (in UE5)? That would be really helpful!

2

You can get a TArray from function without return if you pass an array parameter as non-constant reference. For example:

void GetArray(TArray<AActor*>& Array); // in BP returns an array of Actors
2 Likes
3

I might be wrong, but as far as my understanding is right this would not work since in a UFunction(BlueprintCallable) ‘&’ is not allowed or am I wrong?

I want it to work in a UFunction, C++ alone would not “help” me. ^^

But thank you so much, I am gonna experiment a little with the code you gave me.

4

It is allowed, but in BP it will be treated as an output parameter, so you can’t use it when calling the function like you would in C++;
You can use two array parameters, one as input, the other as output:

UFUNCTION(BlueprintCallable)
void ChangeArray(TArray<int32> InArray, TArray<int32> &OutArray);

And then you can use it like this:
image

1 Like
5

Looks really promising and is working. Thanks a lot. Now, does this work with any Type of TArrays? For example TArray<TSharedPtr>? How would I do that? This is what I couldn’t get to work and I thought I had to use ‘*’ as the compiler said but I didn’t know where nor how.

6

IDK, you need to test it. Not all types of pointers are supported by blueprints.

7

Yea, that seems to be the case for what I was trying to do but thats good to know, thanks a lot to both of you. That helped my understand a little more and I think I might be able to solve what I was trying to do!
Thanks again!

8

To avoid unnecessary array copies you should pass input arrays by const-ref:

UFUNCTION(BlueprintCallable)
void ChangeArray(const TArray<int32>& InArray, TArray<int32> &OutArray);
3 Likes
9

For whatever reason I couldn’t get any of the above solutions to work. I’m also quite new to C++. I was trying to return a TArray of Enums. Here’s the solution that ended up working for me:

//.h
UENUM(BlueprintType)
enum class EWeekday : uint8
{
	Monday,
	Tuesday,
	Wednesday,
	Thursday,
	Friday,
	Saturday,
	Sunday
};

UFUNCTION(BlueprintCallable, Category = "NPCScheduleNode")
TArray<EWeekday> GetWeekdays();

#if WITH_EDITORONLY_DATA

UPROPERTY(EditDefaultsOnly, Category = "NPCScheduleNode")
TArray<EWeekday> Weekdays = { EWeekday::Monday, EWeekday::Tuesday };

#endif

//.cpp
TArray<EWeekday> UNPCScheduleNode::GetWeekdays()
{
	TArray<EWeekday> copyArray = Weekdays;
	return copyArray;
}

And the result in BP:
Capture

Maybe not the best way since I’m making a copy but it’s not my top concern right now and couldn’t get the other methods to work