Access to a variable inside a C# class

Question

Hello everybody,

I'm having trouble accesing a variable inherited from a class.

This is my class:

 using UnityEngine;
     using System.Collections;
     
     public class RecetaInitializer : MonoBehaviour {
     
         public RecetaConstructor[] Receta;
     
         void Start () {
             Receta = new RecetaConstructor[9];
     
             for (int i = 0; i < Receta.Length; i++)
             {
                 Receta[i] = new RecetaConstructor();
             }
     
             Receta[0].AddReceta(1, "Huevo Duro", "agua,huevo");
             Receta[1].AddReceta(2, "Papas Fritas", "papa,aceite");
             Receta[2].AddReceta(3, "Omelette", "huevo,queso,jamon");
             Receta[3].AddReceta(4, "Licuado De Banana", "leche,banana");
             Receta[4].AddReceta(5, "Chocolatada", "leche,chocolate");
             Receta[5].AddReceta(6, "Fideos Con Queso", "fideos,queso");
             Receta[6].AddReceta(7, "Pancho", "pan,salchicha,queso");
             Receta[7].AddReceta(8, "Pizza", "pan,queso,jamon,tomate");
             Receta[8].AddReceta(9, "Hamburguesa", "pan,paty,queso,lechuga,tomate");    
             // Debug.Log(Receta[7].GetRecetaName());
         }
         
     }

Now, I want to access from another script the variable Receta. To achieve this I created another class that I use to manage my game:

 using UnityEngine;
 using System.Collections;
 
 public class MenuGUI : RecetaInitializer{
 
     public RecetaConstructor[] Receta;
     // RecetaConstructor is a class I have which works fine, it lets me create different recipes for my game.
     
     
     void Start()
     {
         Receta = gameObject.GetComponent<RecetaInitializer>().Receta;
         PrepareGame();
     }
     
     private void PrepareGame()
     {
         Debug.Log(Receta[0].GetRecetaName());
         // GetRecetaName() is self-explanatory, given the index it returns the name of the Recipe/Receta
     }
 
 }

I'm clearly missing something here, ad Unity gives me a nice "Object reference not set to an instance of an object".

I also tried by not inheriting the class and add it with AddComponent and then RecetaConstructor[] Receta = gameObject.GetComponent().Receta; But the result is the same.

Any hint? Thanks very much!

Answer 1

Best Answer

Answer by MarkFinn · Nov 21, 2012 at 06:45 AM

Ok, just remove the line

 Receta = new RecetaConstructor[9];

from the start method in RecetaInitializer.

and replace

 public RecetaConstructor[] Receta;

with

 public RecetaConstructor[] Receta = new RecetaConstructor[9];

That line has been blanking your preset data each time.

And make sure to rename your Start() in RecetaInitializer to Awake().

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MarkFinn · Nov 21, 2012 at 06:48 AM 0

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Just to add, unless there's more to the classes than you are showing us then the inheritance is really unnecessary and, frankly, only going to cause confusion.

kevinseligmann · Nov 21, 2012 at 06:52 AM 0

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It's working perfeclty now @markfinn , thank you very much. I still don't understand exactly what the problem was, but I'm looking forward to learn more of it as this was my first attemp at classes.

Also, there's not a lot more that this, I just thought that classes where the way to go on something like this, as I wanted to store data and using 3 different arrays seemed a little odd at the time.

nicloay · Nov 21, 2012 at 06:57 AM 1

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in your first listing problem was that you overrided the method Start(), and didn't call this metod from your derrived class if you want to fix your previous code in MenuGUI class in metod Start at first call base.Start(), so only after that it will cal your Start function of your base class.

kevinseligmann · Nov 21, 2012 at 06:59 AM 0

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thank you very much guys, it's way clearer now

MarkFinn · Nov 21, 2012 at 07:09 AM 1

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One thing to note. The actual problem here was that when two classes on the same object depend on eachother's Start() functions the data will not be set. Start() is done before the first time Update() is run.

If one monobehaviour has data that another will use, make sure that data is done in Awake().

Answer 2

Answer by nicloay · Nov 21, 2012 at 06:34 AM

why do you need to initialize data in Start() looks like you data is hardcoded and static, so just use static initialization

 using UnityEngine;
 using System.Collections;
 
 public class RecetaInitializer : MonoBehaviour {
 
 public static RecetaConstructor[] Receta = new RecetaConstructor[9]{
     new Receta(1, "Huevo Duro", "agua,huevo"),
 new Receta(2, "Papas Fritas", "papa,aceite"),
 new Receta(3, "Omelette", "huevo,queso,jamon"),
 new Receta(4, "Licuado De Banana", "leche,banana"),
 new Receta(5, "Chocolatada", "leche,chocolate"),
 new Receta(6, "Fideos Con Queso", "fideos,queso"),
 new Receta(7, "Pancho", "pan,salchicha,queso"),
 new Receta(8, "Pizza", "pan,queso,jamon,tomate"),
 new Receta(9, "Hamburguesa", "pan,paty,queso,lechuga,tomate")
 };
         
 }

or, if you don't like it, make use getter and setter and in getter just check if you private array=null initialize them.

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kevinseligmann · Nov 21, 2012 at 06:38 AM 0

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Thanks Nikolay, that's definetely a better way of doing it and you're correct that my data is indeed static.

But the problem I have is still happening, whenever I try to access the Receta variable I get a null reference and I really don't know why.

nicloay · Nov 21, 2012 at 06:50 AM 0

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sorry, mixed up a right part of archive initialization, already fixed in the code, must be public static RecetaConstructor[] Receta = new RecetaConstructor[9]{

Access to a variable inside a C# class

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