NullRef bug (reported) | Official Unity Discord | Page 1

green ember Dec 12, 2021, 10:36 AM

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BrickParent https://gdl.space/ecozeroqiv.cpp
Brick https://gdl.space/cobudaponu.cs
LevelManager https://gdl.space/gidosupexo.cs
Ball https://gdl.space/iqozuwarum.cs
GridManager https://gdl.space/ufilabatet.cs

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In the minutes before this error occurred, I was simply adding a Debug.Log() to the Ball's collision exit call

bitter grove Dec 12, 2021, 10:40 AM

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any particular reason you are using FindObjectOfType to get a reference to a singleton? You have a public static reference built right in so just access your LevelManager with LevelManager.Instance

also it seems likely that line 33 in your Brick class is returning null

green ember Dec 12, 2021, 10:40 AM

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Oh, that, I decided to make it static after doing that.

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Maybe that's the problem

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and yes, line 33

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I am perplexed

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this line has not changed, yet it does seem to return null

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this is odd

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the error persists, so parent should be null, yet the game executes perfectly like before

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This is the logic simplified:

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Ball collides with Brick - on Exit, access brick in a static list, use the TakeDamage function with ballDamage input

Brick takes damage, and if 0 or less health, tells the parent it is being destroyed, and disables itself.
The parent then plays the Particle system,
and tells the LevelManager that a Brick has been destroyed, adding to the counter

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This should work, and it is working, but I get bogus errors

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or, as experience tells me, I could be retarded

bitter grove Dec 12, 2021, 10:50 AM

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I see that you are setting the parent of the brick to the GridManager object when you spawn it. Does that object also have the BrickParent component?

green ember Dec 12, 2021, 10:51 AM

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bitter grove Dec 12, 2021, 10:52 AM

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so the brickPrefab object, is that both the parent and brick? if so, just use a serialized reference instead of trying to get the component at runtim

green ember Dec 12, 2021, 10:53 AM

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the prefab contains both objects
The grid manager instantiates the prefab, but Names the Parent and the Child - Capitalized and Lower case

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the parent of the instantiation, is the Grid parent object

bitter grove Dec 12, 2021, 10:53 AM

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then just use a serialized reference to the parent, no need to get component if you can spawn it with a reference to its parent already

green ember Dec 12, 2021, 10:54 AM

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that is a pretty good point

bitter grove Dec 12, 2021, 10:55 AM

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also to make things less confusing and easier to follow the logic, i'd change the brickPrefab field's type to BrickParent so it's a little more obvious what is being instantiated

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you don't have to do that, but i find it's just better practice than using GameObject for the prefab type

green ember Dec 12, 2021, 10:57 AM

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Noted. I try to be practical and use data types other than GameObject, so I don't have to use GetComponent

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in this case, that wasn't directly possible, or maybe with a syntax I haven't considered

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new errors now

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NullReferenceException: Object reference not set to an instance of an object
Brick.OnEnable () (at Assets/Scripts/Brick.cs:33)
UnityEngine.GameObject:SetActive(Boolean)
LevelManager:NewLevel() (at Assets/Scripts/SO/LevelManager.cs:72)
LevelManager:Awake() (at Assets/Scripts/SO/LevelManager.cs:114)

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I have a theory

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I think there is something wrong with the way I've set up the static instance of the LevelManager

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but also - this all worked without errors. I was simply adding a Debug Log to try to fix the problem of a Brick not being registered as destroyed by LevelManager, if the ball was inside it when a new level spawned

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I'm rewriting without static

bitter grove Dec 12, 2021, 11:05 AM

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it's line 33 in the Brick class that is error'd right now, right? Could you tell me what line that is so I can be sure

green ember Dec 12, 2021, 11:05 AM

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parent.BrickIsEnabled();

bitter grove Dec 12, 2021, 11:06 AM

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okay then parent is still null

green ember Dec 12, 2021, 11:06 AM

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but the score counting works, so it does work, but the editor still says error

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did I break my project lol

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we'll see if this works first

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hmm

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NullReferenceException: Object reference not set to an instance of an object
Brick.OnEnable () (at Assets/Scripts/Brick.cs:33)

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Note: I did recreate the Bricks with GridManager

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private void OnEnable()
{
    parent.BrickIsEnabled();

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this is apparently the problem

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public void BrickIsEnabled()
{
    levelManager.BrickSpawned();
}

bitter grove Dec 12, 2021, 11:14 AM

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did you end up making parent a serialized field and dragging the reference in for the prefab?

green ember Dec 12, 2021, 11:14 AM

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yes

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then I recreated the grid's prefabs

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so they are updated

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public void BrickDestroyed()
{
    bricksBroken++;
    bricksRemaining--;

    if (bricksRemaining == 0)
    {
        LevelComplete();
        NewLevel();
    }
}

public void BrickSpawned()
{
    bricksRemaining++;
}

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All this works perfectly fine

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so why am I getting an error, hmm

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If you don't have any other ideas, I'm going to prepare closing about 100 browser tabs before restarting the PC, just in case .Net Framework is derping out

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if you want, I can zip you the project

bitter grove Dec 12, 2021, 11:19 AM

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yeah i have no idea. feel free to zip it up and i'll take a look at it if you want

green ember Dec 12, 2021, 11:19 AM

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Thanks a lot. I'll do that after restart and test.

green ember Dec 12, 2021, 11:42 AM

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I'm about to do just that

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but I can't comprehend why the project is 400 Mb

bitter grove Dec 12, 2021, 11:42 AM

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the library folder is probably the largest part, you can exclude that folder since it gets rebuilt automatically

green ember Dec 12, 2021, 11:42 AM

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ah nice

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📎 NovemberLTS.rar

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Let me know if one of the Brick Sprites is Lighter than the others

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I saved After recreating the grid, and the asset was deleted, so I'm not sure what's going on here

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if it is, just go to the Grid game object and activate the Recreate function by checkbox

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also, don't mind the fugly particle system - I just paused that aspect for a while

bitter grove Dec 12, 2021, 11:59 AM

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yeah i have no idea why this is happening. Like it seems to be affecting several specific bricks, because those same bricks are not being destroyed every single time, but i can clearly see in the inspector that the reference is there.

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gonna try some breakpoints to hopefully get more info about wtf is going on

green ember Dec 12, 2021, 12:00 PM

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doesn't it affect all of them for you?

bitter grove Dec 12, 2021, 12:02 PM

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oh now that i look again, i suppose it does

green ember Dec 12, 2021, 12:02 PM

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if the project is "broken" or any of the classes corrupted, that may have happened while I had the LevelManager also have a static instance - was it correct to have it attached to an object at that point?

bitter grove Dec 12, 2021, 12:03 PM

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yeah you would need to have it attached to an object since it's a monobehaviour

green ember Dec 12, 2021, 12:03 PM

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alright

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So Editor is saying parent.BrickIsEnabled(); doesn't work because of null reference
but the Parent successfully executes BrickIsEnabled(), because the LevelManager is keeping track of the bricks remaining/destroyed

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I created MyParent and MyChild, copied the class contents, changed type accordingly, fixed prefab
No change.

bitter grove Dec 12, 2021, 12:09 PM

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it definitely isn't showing the correct numbers for me. Also for some reason d5 seems to be the only brick that is able to be broken and when it breaks, remaining bricks goes to -1 (from 0)

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but also, why are you instantiating bricks if they are already in the scene?

green ember Dec 12, 2021, 12:10 PM

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your bricks don't break? :S

bitter grove Dec 12, 2021, 12:10 PM

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no, it's because of the nullref, every time a brick is hit it throws the nullref

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oh that's my fault, i messed with the levelmanager a bit

green ember Dec 12, 2021, 12:11 PM

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bitter grove but also, why are you instantiating bricks if they are already in the scene?

To my knowledge, I'm only instantiating them in Editor Mode, once, after setting the parameters.
After that, the objects are simply disabled/enabled

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ah well, that part has worked for some time, even seamlessly when I rewrote it for the List approach

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and TakeDamage etc

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new clue

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or mindfuck

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I believe I forgot to recreate the grid after fixing the prefab, as previously stated

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so I recreated it

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but now it gives an error, and it makes no sense

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it only spawns one brick

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NullReferenceException: Object reference not set to an instance of an object
GridManager.SpawnBricks () (at Assets/Scripts/GridManager.cs:128)
GridManager.Update () (at Assets/Scripts/GridManager.cs:42)

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MY bad

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ignore

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I did this

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wait, my bad again

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hmm

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oh my god, it's class corruption

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I implemented the new scripts with cloned code, correctly across the scripts now

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no errors

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but how can I detect this properly and fix it properly - it's like my project is corrupted now if I can't fix this

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Fixed by recreating classes, copying class contents, rewriting scripts to work with new Class/Type name

bitter grove Dec 12, 2021, 12:24 PM

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wait so you were able to fix it by just recreating everything?

green ember Dec 12, 2021, 12:24 PM

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Yes, the BrickParent and Brick scripts

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I made MyParent and MyChild

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copied contents, rewrote scripts for the new names

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and it works, no errors!

bitter grove Dec 12, 2021, 12:25 PM

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huh weird

green ember Dec 12, 2021, 12:25 PM

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extremely

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this has to be a bug

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but in C# or Unity

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at least I have this zip file and a short description for a solution
Unity should have enough data to work with for a bug report.

green ember Dec 12, 2021, 12:52 PM

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Thanks a lot for the assist @bitter grove

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Have a nice day o/

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NullRef bug (reported)

green ember Dec 12, 2021, 2:22 PM

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The bug is actually back

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Cleaned up some unused code, and all of a sudden, there were errors again, in the new scripts

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currently installing the Unity Editor anew

green ember Dec 12, 2021, 2:59 PM

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After installing the latest LTS, upgrading the project and Regenerating Project Files, the error still persists

strong coral Dec 12, 2021, 5:32 PM

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I have a lot of problems like this too lately. I send a report to unity and am now waiting for answer

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I will keep you up to date when I fix it

green ember Dec 12, 2021, 10:24 PM

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strong coral I will keep you up to date when I fix it

Thanks a lot, man.

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There was a new version out now, up from 23f1 to 24f1
My project was still bugged when I upgraded, but hopefully they fixed -something- for new ones

dawn zodiac Dec 13, 2021, 7:15 AM

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green ember Thanks a lot, man.

are you instantiating gameobjects in edit mode and saving references to them in a monobehavior, and expecting those references to persist into play mode?

green ember Dec 13, 2021, 7:22 AM

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I'll have a closer look

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The grid is sized and filled with Bricks in the Editor
when I enter Play Mode, the Brick components are added to a List in LevelManager

dawn zodiac Dec 13, 2021, 7:23 AM

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if so, i don't think you can really do that? you could instantiate things from edit mode and then save the scene and they would be there, but i don't think references in monobehaviors will carry over between play sessions

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https://docs.unity3d.com/Manual/DomainReloading.html might be the actual culprit of your issue

green ember Dec 13, 2021, 7:24 AM

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it is used by Ball in OnCollisionExit2D to select which ball takes the damage, based on Name

dawn zodiac Dec 13, 2021, 7:24 AM

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you can turn it off, but you have to manage all that stuff yourself

bitter grove Dec 13, 2021, 7:24 AM

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unless I'm misremembering, wasn't the nullref in the OnEnable method for the Brick class and the only object in that method that could be null was the parent object which had a serialized reference

dawn zodiac Dec 13, 2021, 7:24 AM

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alternately, just spawn the stuff in at runtime

green ember Dec 13, 2021, 7:24 AM

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dawn zodiac if so, i don't think you can really do that? you could instantiate things from e...

Can you clarify which references you are referring to?

dawn zodiac Dec 13, 2021, 7:25 AM

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green ember Can you clarify which references you are referring to?

no, because i haven't read through all your code

green ember Dec 13, 2021, 7:25 AM

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Alright.

dawn zodiac Dec 13, 2021, 7:25 AM

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i'm just saying it sounds like that's what you might be doing, so i'm not surprised it's not working

green ember Dec 13, 2021, 7:25 AM

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I've explained a few things earlier in this chat. I'll bring a summary down.

dawn zodiac Dec 13, 2021, 7:25 AM

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you said something about a static list, which is the sort of thing that domain reloading would reset automatically

green ember Dec 13, 2021, 7:26 AM

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I gave the LevelManager a static instance at some point, and beyond that everything worked perfectly.
It was first when I added a Debug Log to Ball OnCollision that I suddenly had this error, which cannot be real if the balls actually take damage

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In my current project there is no static

nova arrow Dec 13, 2021, 7:27 AM

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I don't really know why you've got so much stuff in OnEnable and Awake triggering cross-objects

dawn zodiac Dec 13, 2021, 7:27 AM

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yeah, debug.log isn't what caused your error though, so it makes sense to look elsewhere

nova arrow Dec 13, 2021, 7:27 AM

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these two callbacks interweave between objects, you can only rely on them being before each other when called from the same object

green ember Dec 13, 2021, 7:27 AM

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dawn zodiac yeah, debug.log isn't what caused your error though, so it makes sense to look e...

indeed, but this bug is reproducable, fixable, and reproducable again

dawn zodiac Dec 13, 2021, 7:28 AM

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mmm yeah, could just be a race condition which would explain why you only sometimes see it

nova arrow Dec 13, 2021, 7:28 AM

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BrickParent.BrickIsEnabled is called from Brick.OnEnabled which can very well occur before BrickParent.Awake ever does

green ember Dec 13, 2021, 7:29 AM

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if you download the project zip (50 MB) and create new scripts called MyChild and MyParent, and copy code from Brick and BrickParent, and rewrite the Class names in the code, and rework the prefab, and recreate the grid - then the bug is gone. But later it appears again \o/

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That said, I will for now work with what you are saying.

dawn zodiac Dec 13, 2021, 7:29 AM

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have you stepped through in the debugger? you can see what order things are executing in and confirm that pretty easily

green ember Dec 13, 2021, 7:29 AM

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nova arrow `BrickParent.BrickIsEnabled` is called from `Brick.OnEnabled` which can very wel...

I see. That may be my problem then.

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perhaps this can be solved by disabling the brick in the prefab

bitter grove Dec 13, 2021, 7:32 AM

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you aren't even using the prefab at runtime though

nova arrow Dec 13, 2021, 7:32 AM

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Also, I kinda feel like having ExecuteOnEditMode on GridManager is also asking for trouble

green ember Dec 13, 2021, 7:33 AM

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nova arrow Also, I kinda feel like having `ExecuteOnEditMode` on `GridManager` is also ask...

I'm open to a different approach.
Right now the goal is however not perfection, but results.

dawn zodiac Dec 13, 2021, 7:35 AM

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well what are you trying to solve? why does it execute in edit mode?

nova arrow Dec 13, 2021, 7:35 AM

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I mean, I went back to the singleton, removed ExecuteOnEditMode, and made the bricks spawn in Start

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and problem solved afaik

dawn zodiac Dec 13, 2021, 7:36 AM

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that's how i usually do it, but maybe that's no good, cause you want to see the bricks in the editor or something?

nova arrow Dec 13, 2021, 7:36 AM

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because Start is after Awake, the references are set up, and there's no conflict when trying to find the singleton as it's already set up

bitter grove Dec 13, 2021, 7:36 AM

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damn now i feel dumb for not suggesting that last night

green ember Dec 13, 2021, 7:37 AM

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nova arrow and problem solved afaik

the error is gone?

dawn zodiac Dec 13, 2021, 7:37 AM

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the only downside there is you can't see your bricks until you press play

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but for that i would add a preview button and clean those up before spawning the 'real' ones in playmode, probably?

nova arrow Dec 13, 2021, 7:38 AM

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I'm sure you could fix that by restructuring some other stuff, but I don't have enough understanding of what's going on (nor do I want to) to figure out the 'proper' solution

green ember Dec 13, 2021, 7:38 AM

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private void Start()
{
    // Get Bricks
    bricks.AddRange(grid.GetComponentsInChildren<MyChild>(true));

    // Prepare New Level
    DisableAllBricks();
    NewLevel();
}

I moved this, but the error persists

dawn zodiac Dec 13, 2021, 7:38 AM

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yeah, my more general advice from skimming this is 'your life will be easier if you have your logic only flow in one direction where possible'

nova arrow Dec 13, 2021, 7:42 AM

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I mean, from the uploaded project I did as I said above
changing GridManager to spawn after awake all I did was a lazy

void Start()
{
    recreate = true;
}```
and make sure you delete all the bricks in the scene

green ember Dec 13, 2021, 7:46 AM

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nova arrow I mean, from the uploaded project I did as I said above changing GridManager to ...

this single change to the Grid Manager made all the Null Reference errors in the console go away?

nova arrow Dec 13, 2021, 7:46 AM

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No, it required the other stuff above that I mentioned too

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Though I'm unsure what the issue is at Ball.OnCollisionExit2D (UnityEngine.Collision2D collision) in the Find function, I can't debug it properly

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but that's separate from the other issues

green ember Dec 13, 2021, 7:52 AM

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nova arrow Though I'm unsure what the issue is at `Ball.OnCollisionExit2D (UnityEngine.Coll...

levelManager.bricks.Find(x => x.name == collision.gameObject.name).TakeDamage(ballDamage);

This line finds the name of the brick from the collision, finds it in LevelManger's public List of Brick, and executes the TakeDamage function of that Brick

nova arrow Dec 13, 2021, 7:53 AM

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I figured it out. I clearly don't use Linq enough to have debugged this

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Find on an empty List

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you're trying to invoke the result, which is just null.

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which is only happening because bricks is set up in awake, which could only be correct under the specific engineered circumstances you had earlier

green ember Dec 13, 2021, 7:55 AM

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while I included using Linq, it doesn't seem like it's being used in the script at all, from what my IDE tells me.

I'm only calling the list from OnCollisionExit, which won't happen for a while after starting the game?

nova arrow Dec 13, 2021, 7:56 AM

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as Prakkus said, you should really try to engineer your logic so that it all flows in one direction. You have a lot of initialisation scattered over the place in very similar methods that may or may not execute before or after each other. It's an easy way to create situations where one issue flows onto another and another as moving one point of failure just hits another

nova arrow Dec 13, 2021, 7:57 AM

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green ember while I included using Linq, it doesn't seem like it's being used in the script ...

Yes, this was the only error (in OnCollisionExit2D) that was occuring after I fixed the startup ones.

green ember Dec 13, 2021, 7:58 AM

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Ironically I was starting to* do just that, and was improving, I thought.
But I see I do need a better approach.

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I'm reading through everything that's been said. Need some time to catch up.
Thanks for all the help.

green ember Dec 13, 2021, 8:32 AM

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bitter grove unless I'm misremembering, wasn't the nullref in the OnEnable method for the Bri...

This is correct. From our perspective, it didn't make sense that the parent would be null, since it was a prefab and the parent was active.
I'll post a full report once I'm done working through this.

green ember Dec 13, 2021, 3:26 PM

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I have found the error in my own head

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I was not aware that each object would run both Awake and OnEnable, before the next object's Awake

Assumed all Awake were run before any OnEnable.

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Thanks a lot to everyone for helping out.

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And credit to the friend who gave me the last bit of insight.

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I will pay recompense by watching programming pattern tutorials

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Have a nice day guys o/

#NullRef bug (reported)

I was not aware that each object would run both Awake and OnEnable, before the next object's Awake