C# NullReferenceException when reading array that won't initialize

Question

I am trying to make an editor extension for Unity that reads a class named Attack, but C# is not throwing back a NullReferenceException when try to set the object.

This is where the problem lies:

void OnGUI(){
    EditorGUIUtility.labelWidth = 60;
    GUILayout.Label("Attack Manager", EditorStyles.boldLabel);

    Attacks[DataStrings.Length - 1] = new Attack();
    if (DataStrings != null){
        foreach(string Dataline in DataStrings){
            Attacks[i] = new Attack();
            Attacks[i] = JsonUtility.FromJson<Attack>(DataStrings[i]);
            NewAttack(true);
            i++;
        }
    }

Is the value saved in the array? And can you show where you initialize the array? — Afonso, Jul 02 '18 at 17:45
What is `i`? Which line produces the error? Why check for `null` after using `DataStrings`? — 001, Jul 02 '18 at 17:47
Please clarify your question, you wrote that "but C# **is not** throwing back a NullReferenceException" — Dai, Jul 02 '18 at 17:47
Why `Attacks[i] = new Attack();` and immediately `Attacks[i] = JsonUtility.FromJson(DataStrings[i]);` which makes the first statement unnecessary? — Sani Huttunen, Jul 02 '18 at 17:48
i is a public int within the namespace so that our classes can access it. — ThatDGuy, Jul 02 '18 at 17:48
Please describe "won't initialize." If you need to initialize an array and it "won't initialize," isn't that the problem? — Scott Hannen, Jul 02 '18 at 17:48
@Dai whoops. That was a typo. It **is** throwing back a NullReferenceException. — ThatDGuy, Jul 02 '18 at 17:49
@SaniSinghHuttunen That was me trying something that didn't work. — ThatDGuy, Jul 02 '18 at 17:50
@ThatDGuy: So... On which line is it throwing the exception and where are `Attacks` and `DataStrings` initialized? — Sani Huttunen, Jul 02 '18 at 17:51
@JohnnyMopp i is defined in the namespace because other classes use the variable. Lines using the array return NullReferenceExceptions no matter what. I'm checking for null because DataStrings is being read from a file. — ThatDGuy, Jul 02 '18 at 17:51
@ThatDGuy: `Attacks[DataStrings.Length - 1] = new Attack();`? — Sani Huttunen, Jul 02 '18 at 17:53
@SaniSinghHuttunen It's that as well as the other two lines that reference it. — ThatDGuy, Jul 02 '18 at 17:54
@SaniSinghHuttunen It's being defined within the namespace that the class is located in. — ThatDGuy, Jul 02 '18 at 17:58
@ThatDGuy: I asked where and how it's INITIALIZED... not defined (or declared). — Sani Huttunen, Jul 02 '18 at 17:59

score 0 · Accepted Answer · answered Jul 02 '18 at 17:51

0

Attacks = new Attack[0];

Will initiate your Array. HOWEVER I suggest you replace the array with a list

Initialize it like this

List<Attack> Attacks = new List<Attack>()

Then inside your method

    if (DataStrings != null)
{
    foreach(string Dataline in DataStrings)
    {
    var attack = new Attack();
        attack  = JsonUtility.FromJson<Attack>(DataStrings[i]);
        Attacks.Add(attack)
    }
}

answered Jul 02 '18 at 17:51

Dyna Dave

149
1
5

It's throwing back a NullReferenceException at 'Attacks.Add(attack);' – ThatDGuy Jul 02 '18 at 17:57
Nevermind I figured out why that happened there, but now the line that uses JsonUtility is throwing back the NullReferenceException. – ThatDGuy Jul 02 '18 at 17:59
Change `DataStrings[i]` --> `Dataline` – 001 Jul 02 '18 at 18:02
@JohnnyMopp Aha! There was the problem! Thank you very much! – ThatDGuy Jul 02 '18 at 18:03

C# NullReferenceException when reading array that won't initialize

1 Answers1