Nullreference on mouseHit.collider.name using raycasting

Questions & Answers
1

I am writing a script for camera panning, now everything is working except I get a null reference exception on this line:

} else if (mouseHit.collider.name == null)

this is the code in some more context, the script is not finished yet

	private void FixedUpdate()
	{
		mouseRay = Camera.main.ScreenPointToRay (Input.mousePosition);
		if (Physics.Raycast (mouseRay, out mouseHit)) 
		{
			Debug.Log (mouseHit.collider.name);
			camCol = "" + mouseHit.collider.name;
		} else if (mouseHit.collider.name == null) 
		{
			camCol = "";
		}

		if (camCol == "") 
		{
			transform.Translate (0, 0, 0);
		}

		if (camCol == "leftCam") 
		{
			transform.Translate (-0.1f * panSpeed, 0, 0);
		}

I only ask questions here as a last resort, any help would be greatly appreciated! Also, am I correct in thinking that the output of mouseHit.collider.name is a string?

2

This code is problematic:

else if (mouseHit.collider.name == null)

That’s because “mouseHit” is an object. If it’s null (as in your case), you’ll get a null reference exception when trying to access properties of the object (collider) - simply because the object (mouseHit) doesn’t exist.

The proper way to do this is:

if (Physics.Raycast (mouseRay, out mouseHit)) 
{
    // here, the raycast hit something and mouseHit should be valid.  Just access it as necessary.
}
else
{
    // here, mouseHit will not exist (because the raycast did not hit anything) - don't attempt to access it!
}

And, yes, the mouseHit.collider.name will be a string.