TUnion and TArray

Development Programming & Scripting
1

Hello guys, i’m working on Windows, with branch 4.6.
Here’s some code:

USTRUCT()
struct FDataUnion
{
	GENERATED_USTRUCT_BODY()
	TUnion<FVector, UObject*> Union;
};

USTRUCT()
struct FCommandInfo
{
	GENERATED_USTRUCT_BODY()
	TArray<uint32> UnitIds;
	FDataUnion Data;  //simple union
};

In a UObject derived class, this compiles without problem, but if i try to make an array:

USTRUCT()
struct FDataUnion
{
	GENERATED_USTRUCT_BODY()
	TUnion<FVector, UObject*> Union;
};

USTRUCT()
struct FCommandInfo
{
	GENERATED_USTRUCT_BODY()
	TArray<uint32> UnitIds;
	TArray<FDataUnion> Data;  //array of unions
};

i get this strange compiling error:

 [17/17] Link UE4Editor-Impero.dll
1>    Creating of library  ****\Intermediate\Build\Win64\ImperoEditor\Development\UE4Editor-Impero.lib and the object ****\Intermediate\Build\Win64\ImperoEditor\Development\UE4Editor-Impero.exp ...
1>Impero.generated.cpp.obj : error LNK2001: unresolved external symbol "struct FLogCategoryLogUnion LogUnion" (?LogUnion@@3UFLogCategoryLogUnion@@A)
1>****\Binaries\Win64\UE4Editor-Impero.dll : fatal error LNK1120: 1 external not solved

(note, i slightly modified and translated the output)

It’s the first time i find thiss error, and there’s no info about it.
Even removing the USTRUCT macros from FDataUnion doesn’t help.

2

A TArray (of the first version, with simple union) works instead.

3

Not any particular reason, i’m just testing some stuffs. I’ll try to add UPROPERTYs

4

I’ll send it on a server replicated function, so i don’t want the transient flag :slight_smile:

Anyway, i can’t set the UPROPERTY on FDataUnion::Union, it states

Unrecognized type ‘TUnion’

5

The error suggest that your are using a log incorrectly but nothing related to your structs. Is there any reason why you are not using UPROPERTYs?

6

If you do not want to serialize the content of the properties, if they are only populated and used in runtime, you can use the transient property flag.

7

:smiley: so it’s working?

8

Do you use ‘LogUnion’ somewhere? It seams to be a UE_LOG category.

9

i forgot: it requires ofc his include:

#include "Union.h"
10

No moss, i already had the include, i forgot to mention it if someone wants to try the code :slight_smile:

The situation didn’t change :frowning:

11

Nope. Just created this 2 structs. I just have it in my class to test if it compiles with a

TArray<FCommandInfo> t;

But i added it later, the problem is present just declaring those structs as they are written in here

12

I’ll make a test this afternoon and post my results ^^

13

ok, now this is strange:

using this struct

USTRUCT()
struct FDataUnion
{
	GENERATED_USTRUCT_BODY()
	TUnion<FVector, UObject*> Union;
};

in another struct with an array, like this:

USTRUCT()
struct FCommandInfo
{
	GENERATED_USTRUCT_BODY()
	UPROPERTY()
	TArray<FTempStruct> Data;
};

will generate the compile error just with the declaration, but if we use it directly in a class like this:

UCLASS()
class UCommand : public UObject
{
	GENERATED_BODY()
public:
	TArray<FDataUnion> t;
};

will work.

14

I’m going to look closely at the TUnion declaration.

15

Meanwhile, thank you for your interest Moss :slight_smile:

16

The log category is declared in Union.h:

DECLARE_LOG_CATEGORY_EXTERN(LogUnion, Log, All);
17

Aaaaaand that’s it.

in Union.cpp:

// Seemingly not used, because it doesn't compile!
//#include "Union.h"

//DEFINE_LOG_CATEGORY(LogUnion);

we have a log category non fully defined.

18

So, i found out the problem:

Union.cpp is fully commented out, so we’re missing the Log category implementation.

In fact, adding the line

DEFINE_LOG_CATEGORY(LogUnion);

in my class cpp file allowed it to compile without errors.

I suggest to check out and fix the Union.cpp file.

19

It doesn’t work even uncommenting Union.cpp

Then maybe remove the log category?

20

Is there a way i can open a ticket, or it must be a staff member to open it?