Nested Array crashing

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#1

i have a private member of type:
TArray<TArray<class AActor*> > m_2DArray;
or a 2 dimensional array of AActors…
The game works fine but after a minute or so the game just crashes!
on a different lines but all related to access to m_2DArray…notice the same lines worked before and suddenly not.
i do a null check on an actor in the array so its not an actor.
how ever it seems that the member m_2DArray itself is being garbage collected…
I read somewhere that unreal does not support nested arrays but i can not find an official explanation.
Does someone knows it for sure ?

it always crashes about one minute after begin play on one of the access lines to the member…
here is the code:

void UMicroGridComponnet::Fill()

{

FVector l_Location = m_GridLocation;

l_Location.Z += m_CollisionSize.Z*m_AmountOfTiles*2;

l_Location.Y -= m_GridSize.Y - m_GridSize.Y/m_AmountOfTiles;

for (uint8 Columns = 0; Columns < m_AmountOfTiles; ++Columns)

{

    for (uint8 Rows = 0; Rows < m_AmountOfTiles; ++Rows)

    {

        UE_LOG(LogTemp, Warning, TEXT("Create Tile Row: %d  Column: %d"),Rows,Columns);

        m_TileArray[Rows][Columns] = m_TileFactory->CreateRandomColorTileAtLocation(l_Location);

    }

    l_Location.Y += m_GridSize.Y/m_AmountOfTiles*2 ;

}

}

void UMicroGridComponnet::Discard()

{

for (uint8 Columns = 0; Columns < m_AmountOfTiles; ++Columns)

{

    for (uint8 Rows = 0; Rows < m_AmountOfTiles; ++Rows)

    {

        if( m_TileArray[Rows][Columns] != NULL)

        {

            m_TileArray[Rows][Columns]->Destroy(true,true);

            m_TileArray[Rows][Columns] = NULL;

            UE_LOG(LogTemp, Warning, TEXT("Destroy Row: %d  Column: %d"),Rows,Columns);

        }

    }

}

}

#2

I’ll take a look into this later today (hopefully)

It does not support UPROPERTY for a 2D TArray last I recall, that includes for garbage collection. Workaround I heard was to split it into a separate struct e.g.

USTRUCT()
struct ActorArray2D
{
    GENERATED_BODY()

    UPROPERTY()
    TArray<AActor*> Array;    
};

// some other class
UPROPERTY()
TArray<ActorArray2D> Array;
#3

If you aren’t resizing your array before doing any of that you are going out of bounds doing

m_TileArray[Rows][Columns]

As both would be empty.

P.S. Your loop has the wrong variable names, Rows would be the outer loop not the inner.

#4

Hi Dan,
I resized the arrays in the CTOR, other wise it would not work for a minute before.
Regarding the loop it can work both ways as tile factory will adjust the location automatically if space is occupied by another tile.
I write another class for 2D arrays and overload the subscript operator, it seems it the only solution…
Can i write a templated class in unreal?

Thanks

#5

Yes but I don’t think you can for UCLASS which I assume is the issue with having a nested array(?). A quick search gives me this
https://forums.unrealengine.com/development-discussion/c-gameplay-programming/1750331-template-uclass-or-an-other-way

#6

I tried the USTRUCT solution but game crashes when accessing Tarray ,(note it works fine and after a few moments it just crashes while accessing Tarray ).
I Have Null Checks every where…it crashes in lines after i checked for Null already :frowning:
I double checked i don’t go out of bounds when using the subscriptor… i initialized the array correctly.
I removed TArray and it’s not crashing…??? I trying to understand what am i doing wrong…
So I tried using one dimensional array but still crashes(again it works for a few moments but after about a minute it crashes while accessing Tarray).
So here i was sure somehow Tarray is responsible but i investigated a bit further and found some suggestion online… i wrote this in the h file
UPROPERTY()
TArray<TWeakObjectPtr > m_TileArray;
and this to cpp
if( m_TileArray[Rows + m_AmountOfTiles* Columns].IsValid())
the game is still crashing…LOL i fill like i’m fighting unreal instead of making games…

#7

It sounds like the actors are being garbage collected but I’m not sure why that would be the case. If you want I could take a look at it if you are willing to send your project?

#8

I’m just venting a little bit :laughing:, anyway thanks for hearing me complaining all the time :sweat_smile:
Thanks for the offer how can i send you my project? c++ files wont be enough, i have assets needed for the projects.

#9

File > Package Project > Zip up project

#10

How should i send the zip file? Email?

#11

Wherever, here, PM, email.

#12

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