Another NullReferenceException error.

Questions & Answers
1

What should be happening is “Game Over” appearing upon player death, but when the script is called, it tells me theres no reference to an object. But i have it set in the inspector as a text element. And none of the scripts return a bug, so everything is “correct.” This is the error I’m getting exactly. I’ll reference what the trouble lines are with comments.

NullReferenceException: Object reference not set to an instance of an object
playerHealth.Death () (at Assets/Scripts/playerHealth.cs:86)
playerHealth.TakeDamage (Int32 amount) (at Assets/Scripts/playerHealth.cs:77)
AsteroidDmgMed.OnTriggerEnter2D (UnityEngine.Collider2D other) (at Assets/Scripts/AsteroidDmgMed.cs:23)

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class GameController : MonoBehaviour 
{
	public Vector3 spawnValue;
	public GameObject[] hazard;

	public int hazardCount;
	public float spawnWait;
	public float waveWait;
	public float startWait;
	int randHazard;

	public Text gameOverText;
	public Text restartText;

	private bool gameOver;
	private bool restart;



	void Start () 
	{
		gameOver = false;
		restart = false;
		restartText.text = "";
		gameOverText.text = "";
		StartCoroutine (SpawnWaves ());
	}

	void Update ()
	{
		if (restart) {
			if (Input.GetKeyDown (KeyCode.R)) {
				UnityEngine.SceneManagement.SceneManager.LoadScene ("Main");
			}
		}
	}
	
	IEnumerator SpawnWaves ()
	{
		yield return new WaitForSeconds (startWait);
		while (true) {
			for (int i = 0; i < hazardCount; i++) {
				randHazard = Random.Range (0, 3);
				Vector3 spawnPositionXpos = new Vector3 (spawnValue.x, Random.Range (-spawnValue.y, spawnValue.y), spawnValue.z);
				Vector3 spawnPositionXneg = new Vector3 (-spawnValue.x, Random.Range (-spawnValue.y, spawnValue.y), spawnValue.z);
				Vector3 spawnPositionYpos = new Vector3 (Random.Range (-spawnValue.x, spawnValue.x), spawnValue.y, spawnValue.z);
				Vector3 spawnPositionYneg = new Vector3 (Random.Range (-spawnValue.x, spawnValue.x), -spawnValue.y, spawnValue.z);
				Quaternion spawnRotation = Quaternion.identity;
				Instantiate (hazard [randHazard], spawnPositionXpos, spawnRotation);
				Instantiate (hazard [randHazard], spawnPositionXneg, spawnRotation);
				Instantiate (hazard [randHazard], spawnPositionYpos, spawnRotation);
				Instantiate (hazard [randHazard], spawnPositionYneg, spawnRotation);
				yield return new WaitForSeconds (spawnWait);
			}
			yield return new WaitForSeconds (waveWait);

			if (gameOver) {
				restartText.text = "Press 'R' to Restart";
				restart = true;
				break;
			}
		}
	}

	public void GameOver ()
	{
			gameOverText.text = "Game Over";
			gameOver = true;
	}
}

using UnityEngine;
using UnityEngine.UI;
using System.Collections;

public class playerHealth : MonoBehaviour
{
	public int startingHealth = 100;                            
	public int currentHealth;                                   
	public Slider healthSlider;                                
	public Image damageImage;
	public Image healImage;
	public float DmgflashSpeed = 5f;
	public float HealflashSpeed = 5f;
	public Color DmgColor = new Color(1f, 0f, 0f, 0.1f);
	public Color HealColor = new Color (0f, 1f, 0f, 0.1f);

	playercontroller playerMovement;
	GameController controller;

	bool isDead;                                               
	bool damaged;
	bool healed;


	void Awake ()
	{
		controller = GetComponent <GameController> ();
		playerMovement = GetComponent <playercontroller> ();
		currentHealth = startingHealth;
	}
		
	void Update ()
	{
		if(damaged)
		{
			damageImage.color = DmgColor;
		}
		else
		{
			damageImage.color = Color.Lerp (damageImage.color, Color.clear, DmgflashSpeed * Time.deltaTime);
		}

		damaged = false;

		if (healed) {
			healImage.color = HealColor;
		}

		else {
			healImage.color = Color.Lerp (healImage.color, Color.clear, HealflashSpeed * Time.deltaTime);
		}

		healed = false;
	}
		
	public void HealDamage (int amount)
	{
		if (currentHealth == 100) {
			healed = false;
		}

		if (currentHealth < 100) {
			healed = true;
			currentHealth += amount;
			healthSlider.value = currentHealth;
		}
	}

	public void TakeDamage (int amount)
	{
		damaged = true;
		currentHealth -= amount;
		healthSlider.value = currentHealth;

		if(currentHealth <= 0 && !isDead)
		{
			Death ();    //Line 77
		}
	}


	public void Death ()
	{
		isDead = true;
		playerMovement.enabled = false;
		controller.GameOver ();             //Line 86

		}
		
	}

 using UnityEngine;
 using System.Collections;

 public class AsteroidDmgMed : MonoBehaviour {

public int asteroidMedDmg = 10;

GameObject player;
playerHealth PlayerHealth;

void Awake ()
{
	player = GameObject.FindGameObjectWithTag ("Player");
	PlayerHealth = player.GetComponent <playerHealth> ();

}

void OnTriggerEnter2D(Collider2D other)
{
	if (other.gameObject == player) 
	{

		PlayerHealth.TakeDamage (asteroidMedDmg);  //Line 23
	}

}

}

2

If you have attached a Text Component in the inspector, don’t forget to get that component of your object with:

gameOverText = GetComponent<Text>();

This will make sure you are writing to the right text component. What I’m thinking is that you are writing text to non-existing (null) text component, what will give you a “null reference exception” error.

3

That will not worksince your playerHealth and controller scripts are on different objects. In your playerHealth script in the Awake() method, this line here attempts to get the controller component from the object it is on:

controller = GetComponent <GameController> ();

Since there is no controller on that object, it is null, which is why when you call controller.GameOver(), you get a null reference.

Put the controller on the same object as the playerHealth and it would work. Alternatively, and a method more commonly used, is to create a tag for the controller. If you called that tag Controller, you could then get the reference to the object in that Awake() method by using this code:

controller = GameObject.FindWithTag("Controller").GetComponent<GameController>();