Initialization inside Start() or Awake()?

I've found that sometimes when declaring my variables in C# I get errors. Sometimes moving the lines inside "Start()" fixes the error. How do you determine what needs to be initialized within Start or Awake?
Thanks,
-C not so sharp

 

I should have asked that question differently. Not quite sure how to construct it though. Let me show in code:

This code works. Figure A.

Code (CSharp):

1.  
2. Vector3 myVariable = new Vector3(0,0,0);
3.  
4. void Start(){
5.  
6. }
7.  

This will throw an error. Figure B.

Code (CSharp):

1. public GameObject myCamera;
2.  
3. Vector3 myVariable = myCamera.transform.position;
4.  
5. void Start(){
6.  
7. }

This is correct code. Figure C.

Code (CSharp):

1. public GameObject myCamera;
2.  
3. void Start(){
4. Vector3 myVariable = myCamera.transform.position;
5. }

error Figure D.

Code (CSharp):

1.  
2. var myVariable = 10;
3. void Start(){
4.  
5. }

no error Figure E.

Code (CSharp):

1.  
2. void Start(){
3. var myVariable = 10;
4. }

Is this because in Figure A. the stack declares myCamera at the same time and not before myVariable? If that were true how come figure D. throws errors and not E.? And why does Figure A. work while D throws an error?

Thanks

 

Because the last one you are using primitives types.
In the first ones, the gameObject won't let you assing those things outside of Awake or Start.

 

Do internal initialization in Awake and initialization that relies on other GameObjects in the scene in Start. Awake is called after the object is fully initialized and Start is called after *every* object is.

 

About example A,B and C: You cannot use the currently created instance for field initialization outside of functions. Since the transform property is a (disguised) instance method, you cannot use it. And even if you could, reference values might not even be initialized yet; which would result in null reference exceptions. Here is some documentation from Microsoft.

About samples D and E: In C#, you can only use the var keyword in local scope; basically methods only. So that should explain it. See the link for a more detailed description about it.

 

So primitive data types must me initialized within a function? Is this C# specific? (or javascript as well?)

Mr. Mud: So primitive data types must be initialized within a method? Thanks, very helpful!

 

Not quite. You can access static fields/methods (this includes fields marked as const(ant)); even outside of methods.

Values assigned to other instance fields, or that you retrieve from methods/properties cannot be assigned outside of functions.

 

No.
What I meant to say is that it did work because you use primitives.
Your real problem in D is that you said your myVariable is of type VAR. If you want to create the variable outside of the Start or Awake method, you need to specify the type (int, float, etc).

If I'm not mistaken.

 

No you don't. This works fine.

Code (csharp):

1.  
2. public class SomeClass : MonoBehaviour
3. {
4.     var someList = new List<GameObject>();
5. }
6.  

This is bad

Code (csharp):

1.  
2. public class SomeClass : MonoBehaviour
3. {
4.     var someList;
5.  
6.     void Awake()
7.     {
8.         someList = new List<GameObject>();
9.     }
10. }
11.  

 

Usually I initialize variables in Awake and do things with them in Start. This way, I never see any null reference exceptions even when communicating with other scripts.

 

Thanks, I'll have to try that

 

I have found this was confusing for me:
In a new created script there is a comment for Start - "use this for initialization". And there's no Awake.
But in the documentation for Start() and Awake() stays that sometimes initialization should be done in Awake and sometimes in Start.

 

As previously mentioned it depends on what you would like to initialize.
Local script stuff that could be accessed by other scripts = awake
Anything else plus stuff that uses external (to the script) references = start