NullReferenceException: Object Reference not set to an instance of an object

Question

this is the error i get when i try to run my code. I'm trying to make a whole bunch of fences disappear. All the fences are parented to one empty child object, so i don't have to individually remove each one of them.

I'm calling the function to remove the fences here:

 function canPurchase ()
 {
     if (totalScore >= 50)
     {
         totalScore -= 50;
         GameObject.Find("pitVendorRaycast").GetComponent(pitVendorRay).purchase();
         GameObject.Find("pitBoudary").GetComponent(pitPurchased).purchased(); //code to call function
     }
 }

and actually running the function here:

 #pragma strict
 
 function purchased ()
 {
     renderer.enabled = false;
 }

Answer 1

GameObject.Find() if it doesn't find anything, it will return null. So you're trying to call null.GetComponent() which will not happen. Also even if Find() finds something every time, maybe this something, lacks the component pitVendorRay. You should do the following:

 var foundGameObject = GameObject.Find("pitVendorRaycast");
 if (foundGameObject!=null)
 {
      var rayComponent = foundGameObject.GetComponent(pitVendorRay);
      if (rayComponent!=null)
           rayComponent.purchase();
      else
           Debug.Log("The object "  + foundGameObject + " doesn't have a pitVendorRay Component");
 }
 else
      Debug.Log("Could not find an object with name pitVendorRaycast");

The reason it returns null, is maybe because you have a different name in the object, or because you forgot to add a component. To make sure that you have a component, you can write the following attribute in C#:

 [RequireComponent(typeof(pitVendorRaycast))]

write this on a C# script and attach this script to the object. If it lacks the component, unity will create a componenet of pitVendorRaycast and add it to the same object that has this attribute. more on attributes here and better here.

On a side note, GameObject.Find() is kinda slow and you should avoid it. Instead, you have multiple options: 1)if it's just one object that you need to find, and it always exists, make a variable like that: GameObject objectToFind; and in the editor, you will see this variable on the inspector. You can drag n drop from the hierarchy the object that you wanted to find. 2)if it's multiple objects, you can use a collection of them to store them. For example, let's say that you want to stop all bullets in the scene. Every time that you create a bullet, you should add it to a collection:

 var newBullet = Object.Instantiate(Bullet); //you create a new bullet
 //have a collection, for example a list, by including System.Collections
 //public List<Bullet> bulletList;
 //this should be in a class somewhere
 //bulletList = new List<Bullet>();
 //write the above in a start function of the same class
 //then every time you create a new bullet
 bulletList.Add(newBullet);

and afterwards you can go through each bullet, without having to find them with foreach:

 foreach(Bullet bullet in bulletList)
 {
     bullet.FindAComponenetOrSomething();
 }

NullReferenceException: Object Reference not set to an instance of an object

1 Reply

Your answer

Welcome to Unity Answers

Follow this Question

Related Questions