Unity C# How do I change a variable from a different class?

Question

How do I change the variable in another class?

public class Manager : MonoBehaviour {

    public bool isDead = false;


    void Start () {


        GameObject Slugbert = (GameObject)Instantiate(Resources.Load("Slugbert"));

    }


    void Update () {



    }
}

I'm trying to change the isDead boolean from false to true.

using UnityEngine;
using System.Collections;
using System;

public class Health : MonoBehaviour {






    public GameObject obj;

    Manager manager;

    public int maxHealth = 10;
    public int health = 10;
    public GameObject deathInstance = null;
    public Vector2 deathInstanceOffset = new Vector2(0,0);


    void Start () {
        manager = obj.GetComponent<Manager>();
        health = maxHealth;
    }

    void Update () {

        if (Input.GetKey ("up")) {

            Debug.Log ("Self Destruct Activated");
            TakeDamage();


        }

    }

    public void TakeDamage()
    {



        health -= 100;

        if (health <= 0)
        {


            OnKill();
            Debug.Log ("Running it");

        }
    }

    public void OnKill()
    {

        manager.isDead = true;
        Debug.Log(manager.isDead);


        if (deathInstance) {
            var pos = gameObject.transform.position;
            GameObject deathObject = Instantiate (deathInstance, new Vector3(pos.x + deathInstanceOffset.x, pos.y + deathInstanceOffset.y, pos.z), Quaternion.identity) as GameObject;
        }


        Destroy(gameObject);
    }





}

I've added in a debug.log showing the value of manager.isDead, and it's printing true, however in the inspector when I run it and click on GameControl, the object containing Manager.cs it shows that isDead = false. I'm not sure how I get the value of isDead in GameControl Manager.cs to equal true.

Thanks, I'm pretty new to Unity

possible duplicate of [What is a NullReferenceException and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — O. R. Mapper, Oct 11 '14 at 12:03
@O.R.Mapper Not every `NullReferenceException` has the same scenario. — Shaharyar, Oct 11 '14 at 12:15
@Shaharyar: When there is a `NullReferenceException` on the line `manager.isDead = true;`, there is only one possible scenario, namely `manager` being `null`. The OP doesn't seem to get to that conclusion, so their question boils **exactly** down to the question I linked - "What does this mean, and what can I do about it?" — O. R. Mapper, Oct 11 '14 at 12:19
@O.R.Mapper I just meant we should point out the actual problem there causing the exception. — Shaharyar, Oct 11 '14 at 12:48

score 0 · Answer 1 · answered Oct 11 '14 at 12:05

0

The manager property is not set yet in the class Health.

Change Manager manager; into Manager manager = new Manager();

You are not changing a variable from another class but you are changing the property of an object of a certain class.

answered Oct 11 '14 at 12:05

Barry

3,683
1
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25

This is fixing the error but it's not changing the variable – Zoomz09 Oct 11 '14 at 12:10
What do you mean by changing a variable. The object of class Health has a property manager which is an object of class Manager. With this modification you can now set the property isDead of this property. – Barry Oct 11 '14 at 12:18
How do I do that though? – Zoomz09 Oct 11 '14 at 13:30

score 0 · Answer 2 · answered Oct 11 '14 at 16:30

Your description is unclear. So here two possible variants of what you are trying to do:
1. You have two objects in scene and on the first you attached Manager.cs and on the second you attached Health.cs.
Solution in this case:
a. in Health.cs modify Manager manager; -> public Manager manager; ( in that case you wil be able to se a field in inspector when you choose the second object.
b. Select the second object in scene, lock (press small lock icon) inspector
c. Select the first object and drag&drop it to the Manager field of the second object.

2. You have one object and both scripts attached to it.
Solution:
add to Start function in Health.cs
void Start () { health = maxHealth; manager = gameObject.GetComponent<Manager>(); }

Jay Kazama · Accepted Answer · 2014-10-12T09:42:21.473

The reason you're having that error is because unity doesn't know what this Manager is.
In unity, a script cannot automatically recognize other scripts, even though it is located in the same folder or game object.
In order to access other scripts, you need to assign the variable manager with the actual script manager.cs. Here's how:

Health.cs

// This is the game object where manager.cs is attached to.
// Assign the game object from the inspector, drag drop the game object to this field.
// If manager.cs and health.cs is in the same game object, you don't need this.
public GameObject obj;
Manager manager;

void Start () {
    health = maxHealth;

    // This is where you actually assign manager variable
    // GetComponent<Manager> meaning you want to get a game object component with
    // type Manager, which is your script manager.cs
    // If manager.cs and health.cs is in the same game object, replace "obj" with
    // "gameObject"
    manager = obj.GetComponent<Manager>();
}

And then you should be able to change the variable like you wanted. Hope this helps.

No problem :) I'm just trying to help – Jay Kazama Oct 13 '14 at 08:57 — Jay Kazama, Oct 13 '14 at 08:57

score 0 · Answer 4 · answered Oct 12 '14 at 16:46

0

try to change public bool isDead = false; to

public static bool isDead = false;

in Manager Class and change remaining accordingly

answered Oct 12 '14 at 16:46

Shamseer K

4,964
2
25
43

Unity C# How do I change a variable from a different class?

4 Answers4