Unexpected NullReferenceExecption

I am attempting to create a 2.5d platformer where you can use a grappling hook to move around. The grappling hook is aimed by the cursor. I am trying to make it so you can only grapple onto certain walls. This script is attached to the walls that can be grappled onto:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class WallScript : MonoBehaviour {
5.  
6.     public AttractedScript a;
7.     void Start () {
8.         a = gameObject.GetComponent<AttractedScript>();
9.         Debug.Log (a);
10.     }
11.    
12.     void Update () {
13.        
14.     }
15.    
16.     void OnTriggerEnter(Collider other){
17.         if (other.tag == "Cursor") {
18.             Debug.Log ("1");
19.             a.detect = true;
20.         }
21.     }
22. }
23.  

and this is the script that the detect boolean belongs to:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class AttractedScript : MonoBehaviour {
5.     public GameObject attractedTo;
6.     public float strengthOfAttraction = 5.0f;
7.     public Rigidbody rb;
8.     public bool detect;
9.    
10.     void Start () {
11.         detect = false;
12.     }
13.    
14.     void Update () {
15.         if (detect) {
16.             if (Input.GetMouseButtonDown (0)) {
17.                 rb.useGravity = false;
18.                 Vector3 direction = attractedTo.transform.position - transform.position;
19.                 rb.AddForce (strengthOfAttraction * direction * 20);
20.             }
21.  
22.             if(Input.GetMouseButtonUp(0)){
23.                 rb.useGravity = true;
24.                 detect = false;
25.             }
26.         }
27.     }
28.    
29. }

For some reason, I recive this error "
NullReferenceException: Object reference not set to an instance of an object
WallScript.OnTriggerEnter (UnityEngine.Collider other) (at Assets/Scripts/WallScript.cs:19)"
It surprises me that a is always null despite being assigned gameObject.GetComponent<AttractedScript>. This makes it impossible to grapple. Why might a be null?

 

Unless AttractedScript and WallScript are on the same gameobject, that won't work. gameObject.GetComponent gets the script from the current gameobject, so it's looking for AttractedScript on your wall, which probably isn't what you want.

 

Goonter, thank you for telling me this. What command would allow me to get the script from a different gameobject?