if statement eliminates NRE error?!

Unity Engine
1

(not an issue I’m having, just a super weird behaviour I don’t understand)

Can anyone explain this to me? I’ve had it happen once before on an old project, and I have no clue how it’s happening.

void Start() {

   if (myScriptableObject != null) {
       // whatever code here.
   }
}

I am setting “myScriptableObject” inside another class, right after instantiating the object;

GameObject exampleObject = GameObject.Instantiate(stuff);
exampleObject.GetComponent<SomeClass>().myScriptableObject = someScriptableObject;

What happens if I don’t have the if statement, is it throws a null reference exception, stating “myScriptableObject” is null. But when I do have the if statement, it acts as if it’s not null, and just runs the code inside the if statement.

The only logical thing I can come up with, is that the existence and execution of the if statement gives the game just enough time to assign the value to “myScriptableObject”. This being the only thing I can come up with, makes me worried about whether this could break my game on differently performing computers, causing the code inside the if statement to simply be skipped.

I.e. I’m creating an object through code, then assigning a variable value to it right after. That same value is used in the object’s “Start()” method, inside its own class. If I check for the value being null, the code inside the if statement runs (indicating the value isn’t null), but if the null check isn’t there, I get a Null Reference Exception error.

2

But what is actually going on is that the top code only tests that field, whereas the bottom code is HAIRY CODE and could have failed in either of two places, neither one being the same as what you are testing:

The second code could fail:

  1. exampleObject might be null

  2. exampleObject might not have a SomeClass on it.

How to break down hairy lines of code:

http://plbm.com/?p=248

Break it up, practice social distancing in your code, one thing per line please.

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