Getting a variable into my cloned prefab - Null Reference - C#

Question

Newb question.

I have a Torpedo Launcher that Instantiates a Torpedo from a prefab. The Launcher has a script called 'WeaponControl' attached with a public variable called 'Launch Velocity MPS'.

The Torpedo has it's own script that uses AddForce to start chugging along forward. So the Torp works. BUT, I can't for the life of me get the Launch Velocity MPS variable. Thus it starts really slow. I t$$anonymous$$nk I should be using GetComponent to get the Launch Velocity MPS but I can't even get that to work. All it returns it NULL.

Here is the Torp Script:

 using UnityEngine;
 using System.Collections;
 
 public class TorpThrus : MonoBehaviour {
     public int thrust;
     public Rigidbody rb;
     private WeaponControl launchThrust;
 
     void Start () {
         launchThrust = GetComponent<WeaponControl> ();
         Debug.Log (launchThrust);
         rb = GetComponent<Rigidbody> ();
     }
     
     // Update is called once per frame
     void Update () {
         rb.AddForce (transform.forward * thrust);
     }
 }

And for reference here is the WeaponControl script:

 using UnityEngine;
 using System.Collections;
 
 public class WeaponControl : MonoBehaviour {
     public GameObject weapon01;
     public Transform w1launchPoint;
     public float fireRatePerSecond;
     public float launchVelocityMPS;
 
     public GameObject weapon02;
 
     private float weapon01fired;
 
     // Use t$$anonymous$$s for initialization
     void Start () {
         weapon01fired = 0;
     }
     
     // Update is called once per frame
     void Update () {
 
         bool down = Input.GetKeyDown(KeyCode.Space);
         //bool held = Input.GetKey(KeyCode.Space);
         //bool up = Input.GetKeyUp(KeyCode.Space);
 
         if (down) {
             GameObject projectile;
             projectile = Instantiate (weapon01, w1launchPoint.position, w1launchPoint.rotation) as GameObject;
             weapon01fired++;
             projectile.name = "projectile_" + weapon01fired;
         }
     }
 }

So, how 'should' I solve t$$anonymous$$s issue?

P.S. I'm using Unity 5.3

Answer 1

Best Answer

Answer by vintar · Jan 12, 2016 at 09:12 PM

You could do somet$$anonymous$$ng like t$$anonymous$$s :

 GameObject  projectile = Instantiate (weapon01, w1launchPoint.position, w1launchPoint.rotation)as GameObject;
 projectile.name = "projectile_" + weapon01fired;
 projectile.GetComponent<TorpThrus>().thrust = launchVelocityMPS;

Also, change TorpThrus thrust to a float;

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JediYinYang · Jan 13, 2016 at 12:12 AM 0

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Actually, I was looking for something in the reverse. I want to bring the launchVelocityMPS into the TorpThrust Script since I've also been unable to use AddForce to the projectile with my WeaponControl script. To be clear, what I want is for the torp to be launched at the LaunchVelocityMPS. I don't care which script executes the command. But I want that variable to come from the Laucher, which has the WeaponControl script attached to it.

Also, I don't want to change the LaunchVelocityMPS value from what it's set to in the editor.

Thoughts?

JediYinYang · Jan 13, 2016 at 01:19 AM 0

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Wait, I got it and you sent me in the right direction. Just too much of newb to realize it. I made some changes to the script, but the thing that I had to switch out of the sample you gave me was the .thrust, since I didn't want to alter it. What I did want to alter was the launchThrust.

It'll post the updated scripts below, but thanks for the a help!

The UPDATED Weapon Control Script: using UnityEngine; using System.Collections;

 public class WeaponControl : MonoBehaviour {
     public GameObject weapon01;
     public Transform w1launchPoint;
     public float fireRatePerSecond;
     public int launchForceNewtons;
     private int projectileLaunchForce;
 
     public GameObject weapon02;
 
     private float weapon01fired;
 
     // Use this for initialization
     void Start () {
         weapon01fired = 0;
     }
     
     // Update is called once per frame
     void Update () {
 
         bool down = Input.GetKeyDown(KeyCode.Space);
         //bool held = Input.GetKey(KeyCode.Space);
         //bool up = Input.GetKeyUp(KeyCode.Space);
 
         if (down) {
             GameObject projectile;
             projectile = Instantiate (weapon01, w1launchPoint.position, w1launchPoint.rotation) as GameObject;
             weapon01fired++;
             projectile.name = "projectile_" + weapon01fired;
             Debug.Log ("The launcher's launchNewtons is currently set to: " + launchForceNewtons);
             projectile.GetComponent<TorpThrus> ().launchNewtons = launchForceNewtons;
             projectile.GetComponent<TorpThrus> ().launchedBy = this.name;
         }
     }
 }

The UPDATED TorpThrus Script: using UnityEngine; using System.Collections;

public class TorpThrus : MonoBehaviour { public int thrust; public Rigidbody rb; public string launchedBy; public int launchNewtons;

 void Start () {
     //launchNewtons = GetComponent<WeaponControl> ().launchNewtons;
     Debug.Log ("my name is: " + this.name);
     Debug.Log ("my thrust is: " + thrust);
     Debug.Log ("I was launched by: " + launchedBy);
     Debug.Log ("my Launch Speed is: " + launchNewtons);
     rb = GetComponent<Rigidbody> ();
     rb.AddForce (transform.forward * launchNewtons);
 }
 
 // Update is called once per frame
 void Update () {
     rb.AddForce (transform.forward * thrust);

 }

}

Getting a variable into my cloned prefab - Null Reference - C#

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