List remains null after initialisation?

Questions & Answers
1

Okay, so this is making me feel completely dumb.
I’m making a game in which you can collect things. They have to respawn when the player loses a life.
I have two C# classes. One “Umpire” class that manages things that should be maintained and managed throughout gameplay, and a “Collectible” class, which I’m having a few other classes (“Coin” and “Upgrade”) inherit from.

The Umpire class is attached to a GameObject named “Umpire” in my scene, and my scene contains “Coin” and “Upgrade” objects.

In the Umpire class, I’m making a List of Collectibles that contains all Collectible objects that have been collected during the player’s current life. I want to add to this from the Collectible class upon collision with the player.

The weird thing however, is that this list stays null when I try to add to it, throwing me a null reference exception! Now, this might just be my exhaustion catching up to me, but I just don’t see what I’m doing wrong.

I’ve tried public and private (with getters and setters), static and non-static (because I just want one list, but there will only ever be one umpire object, so either should be fine), but nothing makes a difference.

I even added a useless integer to check whether I could assign and retrieve that, and I can, so there must be something particular with lists going on…

The Umpire class:

using System.Collections.Generic;
using UnityEngine;

public class Umpire : MonoBehaviour
{
    public List<Collectible> collectedDuringThisLife;
    public int indicator;

    private void Awake()
    {
        collectedDuringThisLife = new List<Collectible>();    //List of collected coins. Stays null??
        indicator = 6;
        //DontDestroyOnLoad(transform.gameObject);
    }

    void Update()
    {
    /*
    */
    }
}

The Collectible class

(inherited from by Coin and Upgrade):

using UnityEngine;

public class Collectible : MonoBehaviour { 

    GameObject umpire;
    char letter;

    private void Start()
    {
        umpire = GameObject.Find("Umpire");        // Get the Umpire GameObject from the Scene
        Debug.Log(umpire.GetComponent<Umpire>().indicator);  // Check if the integer is assigned.
                                                                  //It is.
    }

    private void OnTriggerEnter2D(Collider2D collision)
    {
        if(collision.gameObject.tag == "Player")        // If the player touches the collectible
        {
            Debug.Log(umpire.GetComponent<Umpire>().collectedDuringThisLife);//.Add(this);
            //Not adding right now, just checking if exists. Gives nullreference exception either way.
            this.gameObject.SetActive(false);        // Make it disappear
        }
    }
}

So yeah, I’m probably missing something obvious, but I’m at the end of my wits here. Any insight would be greatly appreciated!

2

I wrote up a bit of code that should work, with a static instance of the Umpire class:

public class Umpire
{
    private static Umpire _instance;
    public static Umpire Instance
    {
        get
        {
            if (_instance == null)
            {
                _instance = new Umpire();
            }
            return _instance;
        }
        set
        {
            _instance = value;
        }
    }

    public List<Collectible> collectedDuringThisLife;
    public int indicator;

    Public Umpire()
    {
        collectedDuringThisLife = new List<Collectible>();
        Debug.Log("Instantiated collectedDuringThisLife, this should not be null: " + collectedDuringThisLife);
        indicator = 6;
    }
}

and a updated collectible class:

public class Collectible : MonoBehaviour 
{

    char letter;

    private void OnTriggerEnter2D(Collider2D collision)
    {
        if (collision.gameObject.tag == "Player")
        {
            Umpire.Instance.collectedDuringThisLife.Add(this);
            Debug.Log("Total items collected during this life: " + Umpire.Instance.collectedDuringThisLife.Count);
            this.gameObject.SetActive(false);
        }
    }
}

let me know if this works :slight_smile: