Question Why an initialized attribute still be null in a member method?

My code here:

Code (CSharp):

1. public class SetDefender : MonoBehaviour
2. {
3.     [SerializeField] GameObject gridOnField;
4.     private void Awake() {
5.         print("grid="+gridOnField);
6.     }
7.     public Vector2 GetPointer() {
8.         Vector2 clickPos = new Vector2(Input.mousePosition.x, Input.mousePosition.y);
9.         Vector2 worldClickPos = Camera.main.ScreenToWorldPoint(clickPos);
10.         Vector2 spawnPoint = new Vector2(Mathf.Clamp(Mathf.RoundToInt(worldClickPos.x),1,9),
11.                                                 Mathf.Clamp(Mathf.RoundToInt(worldClickPos.y),1,5));
12.         return spawnPoint;
13.     }
14.     public void SpawnDefender( GameObject defender) {
15.         print("grid="+gridOnField);
16.         if(gridOnField.GetComponent<Grid>().GetTileAccess(GetPointer())!=null) {
17.             print("accessing");
18.             Instantiate(defender,GetPointer(),Quaternion.identity);
19.             gridOnField.GetComponent<Grid>().TakenTile(GetPointer());
20.         }
21.     }
22. }

When I call SpawnDefender from other class, the second "print" line gives NULL, even I did drag and drop the grid object in the field. Why? Thank you for reading and answering. Pls ask me anything if the question is not clear enough.

 

I'm sorry, I found the problem. The one that called Spawndefender was a prefab, which can not assign an in-field GameObject as SerializeField. Therefore, I must assign it by a call inside SpawnDefender.

 

Good find. Scene stuff can refer to prefabs / assets, but never the other way around.

Also, just as a heads up about hairy code like this:

and

You really want to avoid that kinda code!

If you have more than one or two dots (.) in a single statement, you're just being mean to yourself.

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.

"Programming is hard enough without making it harder for ourselves." - angrypenguin on Unity3D forums

"Combining a bunch of stuff into one line always feels satisfying, but it's always a PITA to debug." - StarManta on the Unity3D forums