Question trying to instantiate a prefab, then assign it to a variable (C#)

so I'm trying to instantiate a prefab "T2bullet", and then assign it to the variable "bullet".

here's the code snippet:

Code (CSharp):

1. if(ShotTier == 3) {
2.             Instantiate(T2bullet, PreviewPoint.transform.position, Quaternion.identity);
3.             bullet = GameObject.Find("bullet3").gameObject;
4.         }

unity is saying that the variable isn't set to an object even though I set it to the object.
"NullReferenceException: Object reference not set to an instance of an object"

 

All you need is this:

Code (CSharp):

1. bullet = Instantiate(T2bullet, PreviewPoint.transform.position, Quaternion.identity);

No need to bring an expensive and fragile GameObject.Find() operation into the mix.

 

wait, you can do that?

also, what do you mean by "expensive and fragile"?

 

If you look at the documentation for Instantiate, it says it returns the created GameObject.

GameObject.Find()

pretty much loops through every object in your scene, which can get expensive. What he means by fragile, is just a guess, but if you change the name of the object at all or spell something wrong your code will break.

 

Yes of course you can do that. It would be absolutely silly if you could not. An analogy for trying to use GameObject.Find for this is like:

Imagine you walked up to a gumball machine, you put in a quarter, and let the gumball you just bought fall into a huge pile of gumballs on the floor. Then you spent the next 10 minutes sorting through the pile on the floor searching for the one you just bought.

You could have just grabbed the gumball as it was dispensed from the machine instead, which is what my example code does.

As for the "expensive and fragile" comment:

Expensive: it searches all the objects in the scene for an object with the name you're looking for
Fragile: If you change the name of the prefab or just misspell the name, it won't work.

 

Everytime someone use GameObject.Find everyone forget question and focus only on that.In your code you instantiate bullet but on third line you try to assign GameObject bullet to some other gameobject called "bullet3" in your scene so do this :

Code (CSharp):

1. public class UnityForum : MonoBehaviour
2. {
3.     public GameObject T2bullet;
4.     Transform PreviewPoint;
5.     GameObject bullet;
6.     int ShotTier;
7.  
8. void Start()
9.     {
10.         if (ShotTier == 3)
11.         {
12.             bullet = Instantiate(T2bullet, PreviewPoint.transform.position, Quaternion.identity);
13.             bullet.transform.tag = "Test";  // You can use anything you need on that instantiated bullet
14.         }
15.  
16.     }
17. }

With this code on line 12 you will set things to instantiated bullet and not to some other gameobject.

 

GameObject.Find(string) also requires an exact match, and your bullet was most likely being called "bullet3 (Clone)" after being instantiated.

 

That's because the GameObject.Find usage in the OP is central to the problem, for two reasons:

1. OP wasn't even using the correct name, which would have been "bullet 3(Clone)"
2. Even if they used the correct name, GameObject.Find is just as likely to find any "bullet 3(Clone)" in the scene, not just the one that was just instantiated.

Find() is simply not an adequate tool for the task in this case, and that's why we're focusing on it.

 

Remember the first rule of GameObject.Find():

Do not use GameObject.Find();

I'm glad you asked!

More information: https://starmanta.gitbooks.io/unitytipsredux/content/first-question.html