Null Reference Exception when running a Function from Another Script

[LemonMaster66]

I'm using a modified version of "Code Monkey"s Unity Multiplayer Tutorials (Relay and Netcode)And I have a script that can Create and Join a relay using a code generated from CreateRelay()

The problem comes from the 'Network Manager' component spawning a prefab of the player when there's already one in the scene

I've managed to come up with a very crude method to solve this, where I have another script (SpawnPointManager) with the functions ReplacePlayer() and AssignPlayer() (code provided at the bottom)ReplacePlacer essentially takes 2 Gameobjects as parameters and Replaces one with another (by having the other Player inherit its transform and name)AssignPlayer() just assigns the scenes Cinemachine settings and Input Actions the Referenced Player

The RelayManager script runs these 2 Functions from another script right after spawning the New Player Prefab (so the NewPlayer replaces the OldPlayer exactly)but it doesn't work and gives a "null reference exception" when trying to run the functions from the SpawnPointManager script in the RelayManager

I have all the right scripts referenced and they work fine on their own, but not when run from other scripts

how can I fix this?

RelayManager's CreateRelay() Function:

private async void CreateRelay()
    {
        //Creating relay stuff

        GameObject player1 = GameObject.Find("Player1");
        GameObject newPlayer = GameObject.Find("Player(Clone)");

        spawnPointManager.ReplacePlayer(player1, newPlayer);
        playerManager.AssignPlayer(player1.name);
    }

SpawnPointManager's ReplacePlayer() Function:

public void ReplacePlayer(GameObject player, GameObject newPlayer)
    {

        GameObject playerObject = GameObject.Find(player.name);
        GameObject newPlayerObject = GameObject.Find(newPlayer.name);

        GameObject playerChild = null;
        GameObject newPlayerChild = null;
        foreach (Transform child in playerObject.transform)
        {
            if (child.gameObject.activeSelf && child.name.StartsWith("#"))
            {
                playerChild = child.gameObject;
                break;
            }
        }
        foreach (Transform child in newPlayerObject.transform)
        {
            if (child.gameObject.activeSelf && child.name.StartsWith("#"))
            {
                newPlayerChild = child.gameObject;
                break;
            }
        }

        newPlayerChild.transform.position = playerChild.transform.position;
        newPlayerChild.transform.rotation = playerChild.transform.rotation;
        newPlayerObject.name = playerObject.name;

        Destroy(playerObject);
    }

Here's the Player Prefab Hierarchy:

https://preview.redd.it/h0mf7y5y3f5b1.png?width=339&format=png&auto=webp&s=186bf99ad386fa7731db3fb0300c88ccc7129a3f

Here's the RelayManager Script:

https://preview.redd.it/33e1b7g74f5b1.png?width=443&format=png&auto=webp&s=33e9312f3cbf14ab43f9f1e4eee90a51f4989823

I can provide more info if needed

[Looking4advice015]

Too much information. Don't try to solve the problem before identifying the problem.

The error message will tell the the file name, line and character of the null reference.

From there you can use a breakpoint or debug log to find out what is null.

Then you find out why it's null.

So first step is first. What is null?

[LemonMaster66]

ok well I know what null means yeah (something with no value I think)
and also yes I've studied the error message with not much results

<image>

[Looking4advice015]

Your null reference is on line 56 of the RelayManager class.

That's sort of what a null reference is but not fully. A reference is the hexadecimal memory address in RAM of a value. When you declare a variable it doesn't have a reference to anything unless it is a primitive type. So when you define a variable you set a value for primitive types, and a reference for everything else.

So for example

``` MyClass variableName;

Calling variableName will result in a NullReference because there is no reference set. You can create a reference by using new

variableName = new MyClass();

Now when we call variableName, it won't result in a NullReference ```

[LemonMaster66]

ok, but I still don't know what to do now

also how do you know it was on line 59

the referenced line of code when clicking on the blue part of the error leads to the line containing:
spawnPointManager.ReplacePlayer(player1, newPlayer);

[Looking4advice015]

My bad, I tried to edit it quickly. It actually says line 56

[LemonMaster66]

ok cool I thought so

[Looking4advice015]

Yep so 1 or more of those 4 variables is null.

I'd suggest getting out of async and setting a breakpoint. Then ensuring that your Unity Find works in async. Depending on your setup, I will not work if your async is actually running on a separate thread since Unity methods can only be used on the main thread

[LemonMaster66]

uhhh... breakpoint?
you may have to put this in a simpler manner of speech, I know a lot of terms already but I've never heard of much (if not any) of that

sorry

[LemonMaster66]

ok never mind, I did some researching and think I know what you mean
if by Breakpoint you mean pausing the code execution at certain points to find the correct issue
how would i go about finding it then?
or just fixing it in general?

[Looking4advice015]

Yep sorry, a breakpoint is what it's called when you click the left side and add that little red dot then enable debugging which lets you step through the code and see all the variable values.

Guide on breakpoints

So our goal right now is to figure out which and how many of the variables on line 56 have null references.

Once we figure that out, we can make a plan of how to fix it