[Part 15] Adding level up to treasure chest & NullReferenceException

[Nathan]

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Hello,
Near the end of part 15, the treasure chest script was updated and I wanted to add the ability to basically level up the player’s weapon or passives(if no evolution is available) by just calling StartLevelUp from the GameManager. After testing, I started getting a NullReferenceException.

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I then commented out the code I had added and placed a few Debug.log to check what is read and I noticed I get a NullReferenceException with the original script as well(my fault for forgetting to test). This happens when you attempt to pick up a chest without the ability to evolve, and it does not destroy the game object for some reason. I placed my current TreasureChest script below. Thank you.

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[Terence]

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Update 3 May 2024: Fixed an error in the code.

That’s partially an issue with the OpenTreasureChest() function. You can add a couple of extra checks to prevent the NullReferenceException. For the level up logic, you should put it after the foreach loop.

    public void OpenTreasureChest(PlayerInventory inventory, bool isHigherTier)
    {
        // Loop through every weapon to check whether it can evolve.
        foreach(PlayerInventory.Slot s in inventory.weaponSlots)
        {
            
            Weapon w = s.item as Weapon;
            if (!w || w.data == null || w.data.evolutionData == null) continue; // Ignore weapon if it cannot evolve.

            // Loop through every possible evolution of the weapon.
            foreach (ItemData.Evolution e in w.data.evolutionData)
            {
                // Only attempt to evolve weapons via treasure chest evolution.
                if (e.condition == ItemData.Evolution.Condition.treasureChest)
                {
                    bool attempt = w.AttemptEvolution(e, 0);
                    if (attempt) return; // If evolution suceeds, stop.
                }
                 
            }
        }

        // Logic for your level up stuff goes here.
    }

Let me know if this works!

[Nathan]

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Question. Would it be better to use || rather than && when checking if null? Because if only one of the conditions are met, rather than all three, it would continue. I was having this issue yesterday where if the chest was picked up without a full inventory, I would get a NullReferenceException.

public void OpenTreasureChest(PlayerInventoy inventory, bool isHigherTier)
{
    //loop through every weapon to check if it can evolve
    foreach (PlayerInventoy.Slot s in inventory.weaponSlots)
    {
        Weapon w = s.item as Weapon; //if s.item is a weapon, w will hold the weapon, otherwise it will return null

        if (w == null || w.data == null || w.data.evolutionData == null)
        {
            continue; // Ignore weapon if it cannot evolve
        }

        //loop through every possible evolution of the weapon
        foreach (ItemData.Evolution e in w.data.evolutionData)
        {
            //only attempt to evolve weapons by treasure chest
            if (e.condition == ItemData.Evolution.Condition.treasureChest)
            {
                Debug.Log(w.name + " | " + s.item + " | " + e.condition);
                bool attempt = w.AttemptEvolution(e, 0);
                
                //if evolution suceeds
                if (attempt) 
                {
                    return;
                }
            }
        }
    }
    //Open level up screen if weapon cannot evolve
}

[Terence]

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Question. Would it be better to use || rather than && when checking if null? Because if only one of the conditions are met, rather than all three, it would continue. I was having this issue yesterday where if the chest was picked up without a full inventory, I would get a NullReferenceException.

Yup. It will be better. My bad — my logic was wrong. Using || is the right choice.

[Nathan]

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This works! I am working on the logic for implementing leveling up when picking up a chest if evolution is unavailable. I can post it when I have it working. Thank you.

[Nathan]

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I added the logic for leveling up through chests if interested. It works for me and I haven’t found any issues through testing.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using static PlayerStats;

public class TreasureChest : MonoBehaviour
{
    void OnTriggerEnter2D(Collider2D c)
    {
        PlayerInventoy p = c.GetComponent<PlayerInventoy>();
        
        //evolve weapon
        if (p)
        {
            bool randomBool = Random.Range(0, 2) == 0;

            OpenTreasureChest(p, randomBool);
            Destroy(gameObject);
        }
    }

    public void OpenTreasureChest(PlayerInventoy inventory, bool isHigherTier)
    {
        bool evolutionAttempted = false; // Flag to track if any evolution attempt was made
        PlayerStats ps = FindObjectOfType<PlayerStats>();

        //loop through every weapon to check if it can evolve
        foreach (PlayerInventoy.Slot s in inventory.weaponSlots)
        {
            Weapon w = s.item as Weapon; //if s.item is a weapon, w will hold the weapon, otherwise it will return null

            if (w == null || w.data == null || w.data.evolutionData == null)
            {
                continue; // Ignore weapon if it cannot evolve
            }

            //loop through every possible evolution of the weapon
            foreach (ItemData.Evolution e in w.data.evolutionData)
            {
                //only attempt to evolve weapons by treasure chest
                if (e.condition == ItemData.Evolution.Condition.treasureChest)
                {
                    Debug.Log(w.name + " | " + s.item + " | " + e.condition);
                    bool attempt = w.AttemptEvolution(e, 0);
                    
                    //if evolution suceeds
                    if (attempt) 
                    {
                        evolutionAttempted = true; //set flag to true
                        return;
                    }
                }
            }
        }
        //Open level up screen if weapon cannot evolve
        if (ps != null && !evolutionAttempted) 
        {
            ps.level++;//level up player
            ps.experience = 0;
            
            //Determine the players experience cap for the next level
            int experienceCapIncrease = 0;
            if (ps.levelRanges != null)
            {
                foreach (LevelRange range in ps.levelRanges)
                {
                    if (ps.level >= range.startLevel && ps.level <= range.endLevel)
                    {
                        experienceCapIncrease = range.experienceCapIncrease;
                        break;
                    }
                }
            }
               
            ps.experienceCap += experienceCapIncrease; //increase the players experience cap for the next level

            ps.expBar.fillAmount = (float)ps.experience / ps.experienceCap;//update exp bar fill amount
            ps.UpdateLevelText();
            GameManager.instance.StartLevelUp();
        }
    }
}

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