Object reference not set to an instance of an object

Unity Engine
1

I’m a beginner in Unity, I’m following a tutorial book and everything is going well so far, except for this problem. I’m getting the NullReferenceException for this code:

function lightFire()
{
	var campfire : GameObject = GameObject.Find("campfire");	
	var campSound : AudioSource = campfire.GetComponent(AudioSource);
	campSound.Play();

	var flames : GameObject = GameObject.Find("FireSystem");
	var flameEmitter : ParticleEmitter = flames.GetComponent(ParticleEmitter);
	flameEmitter.emit = true;
	
	var smoke : GameObject = GameObject.Find("SmokeSystem");
	var smokeEmitter : ParticleEmitter = smoke.GetComponent(ParticleEmitter);
	smokeEmitter.emit = true;	
		
	Destroy(GameObject.Find("matchGUI"));
	
}

The error points at this line:

	flameEmitter.emit = true;

The lightFire function gets called here:

function OnControllerColliderHit(hit : ControllerColliderHit)
{
	
	if(hit.collider.gameObject == GameObject.Find("campfire"))
	{
		if(haveMatches)
		{
			haveMatches = false;
			lightFire();
		}
		else
		{
			TextHints.textOn = true;
			TextHints.message = "whatever...";
		}
	}
	
}

What happens when I press the Play button: only the sound plays but nothing happens with the particles and the GUI doesn’t disappear.
Any help would be appreciated.

2

you’re missing something… quite literally

var flameEmitter : ParticleEmitter = flames.GetComponent(ParticleEmitter);

aka “get the ParticleEmitter from flames”… check that there is one

var flames : GameObject = GameObject.Find("FireSystem");

aka “find the object called FireSystem”… check that it exists and is spelled exactly “FireSystem” and not firesystem, fireSystem etc.

3

Could you explain this? Check that there’s a Particle Emitter?

Otherwise, the spelling is correct. It’s as you said, something seems to be missing but I don’t know what or where.

4

Your GameObject named FireSystem doesn’t have a ParticleEmitter component attached to it.

To prove it, put this line right before the line causing the error

Debug.Log("Did we find a particle emitter? " + (flameEmitter != null));
5

I got it. The book is a bit old (for Unity 3.5 or something) and the particle system has changed, so I added the Ellipsoid Particle Emitter manually and I no longer get an error, and it now says “True” to the “Did we find a particle emitter?” debug.
Now it still doesn’t work though; the particles are either on or off, the script doesn’t change that. Only the sound works fine but the particles and the Destroy/GUI don’t work and the text hint stays the same before and after picking up the matches.

Am I missing something else? And do I have to remove the Particle System and leave only the Ellipsoid Particle Emitter?

6

I’d use the new system and get the ParticleSystem component and then use the Play() method instead of trying to screw around with individual emitters.