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Object reference not set to an instance (OnTriggerEnter)

Discussion in 'Scripting' started by ItVang, Aug 12, 2022.

  1. ItVang

    ItVang

    Joined:
    Apr 3, 2022
    Posts:
    2
    Hello! I'm pretty new to C# so I decided to create a little pachinko-type game but now I get stuck when the ball enters the box collider and gives an error in the console.

    NullReferenceException: Object reference not set to an instance of an object
    CupScore.OnTriggerEnter (UnityEngine.Collider other) (at Assets/Scripts/CupScore.cs:34)


    Cup scoring script:

    Code (CSharp):
    1. using System.Collections;
    2. using System.Collections.Generic;
    3. using UnityEngine;
    4. using TMPro;
    5.  
    6. public class CupScore : MonoBehaviour
    7. {
    8.     public GameObject ball;
    9.     GameManager gameManager;
    10.     public int score;
    11.     public TMP_Text pointValue;
    12.     // Start is called before the first frame update
    13.     void Start()
    14.     {
    15.         score = Random.Range(1, 100);
    16.     }
    17.  
    18.     // Update is called once per frame
    19.     void Update()
    20.     {
    21.         UpdateTextboxes();
    22.     }
    23.  
    24.     void UpdateTextboxes()
    25.     {
    26.         pointValue.text = score.ToString();
    27.     }
    28.  
    29.     private void OnTriggerEnter(Collider other)
    30.     {
    31.            gameManager.updateScore(score);
    32.     }
    33. }
    34.  

    Game Manager:

    Code (CSharp):
    1. using System.Collections;
    2. using System.Collections.Generic;
    3. using UnityEngine;
    4. using UnityEngine.UI;
    5. using TMPro;
    6.  
    7. public class GameManager : MonoBehaviour
    8. {
    9.     CupScore cupScore;
    10.     public TMP_Text scoreText;
    11.     private int totalScore;
    12.     // Start is called before the first frame update
    13.     void Start()
    14.     {
    15.        
    16.     }
    17.  
    18.     // Update is called once per frame
    19.     void Update()
    20.     {
    21.  
    22.     }
    23.  
    24.     public void updateScore(int score)
    25.     {
    26.        
    27.         scoreText.text = "Score: " + totalScore;
    28.         totalScore += score;
    29.     }
    30. }
    31.  
     
    ItVang, Aug 12, 2022
    #1

  2. MelvMay

    MelvMay

    Unity Technologies

    Joined:
    May 24, 2013
    Posts:
    10,620
    It tells you the error is on line 34 but your code doesn't have a line 34. You should always make sure you post the correct/full script.

    Anyway, this is the most common thing that beginners get caught by with C# on these forums so we have a pinned posted here: https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/

    In your case, it seems it's referring to line 32 above so "gameManager" is null which is expected because you don't set it anywhere. It cannot just automagically know a reference to an instance of the GameManager; you need to set it.
     
    MelvMay, Aug 12, 2022
    #2

  3. ItVang

    ItVang

    Joined:
    Apr 3, 2022
    Posts:
    2
    Thanks for replying, I figured it out. Also, I'm pretty sure the reason why it said the error was declared on line 34 was that I cleared some code after the error was present so that's my bad.
     
    ItVang, Aug 12, 2022
    #3