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Unity - Cant access reference to another script

I am trying to learn how does Unity work and I now struggle with problem that I cannot access script from another script. I was searching on Interner for couple hours, I have tried many options but nothing helped.
I have 2 scripts.
CoinSpawn.cs - attached to Player (I would change it to other object but I dont know yet to which one, because its something that runs in background so it really dont need to be on player)
CollectingCoin.cs - attached to Coin (Coin is object, that its not on game scene on the start, it spawns randomly)
CoinSpawn is script that randomly spawn Instantiate of object Coin. I want to change value of CoinSpawn.currentCoinOnScreen from CollectingCoin. I ve tried
CoinSpawn test = GameObject.Find("CoinSpawn").GetComponent<CoinSpawn>();
and it doesnt work. I also have my both scripts in the same asset folder. What am I doing wrong? Thank you
CoinSpawn.cs
public class CoinSpawn : MonoBehaviour
{
public GameObject coin;
public int maximumCoinPerScreen = 10;
public int currentCoinOnScreen = 0;
private int randomNumber;
private Vector2 spawnPosition;
private void Update()
{
randomNumber = Random.Range(1, 1000);
if(randomNumber >= 0 && randomNumber <= 1 && currentCoinOnScreen != maximumCoinPerScreen)
{
currentCoinOnScreen++;
float spawnY = Random.Range
(Camera.main.ScreenToWorldPoint(new Vector2(0, 0)).y, Camera.main.ScreenToWorldPoint(new Vector2(0, Screen.height)).y);
float spawnX = Random.Range
(Camera.main.ScreenToWorldPoint(new Vector2(0, 0)).x, Camera.main.ScreenToWorldPoint(new Vector2(Screen.width, 0)).x);
spawnPosition = new Vector2(spawnX, spawnY);
GameObject coinObject = Instantiate(coin, spawnPosition, Quaternion.identity);
}
}
}
CollectingCoin.cs
public class CollectingCoin : MonoBehaviour
{
UnityEngine.UI.Text Coins;
public static int totalCoins = 0;
private void Start()
{
Coins = GameObject.Find("Score").GetComponent<UnityEngine.UI.Text>();
}
void OnTriggerEnter2D(Collider2D c2d)
{
if (c2d.CompareTag("Player"))
{
totalCoins++;
Destroy(gameObject);
Coins.text = "COINS: " + totalCoins.ToString();
// TESTING
CoinSpawn test = GameObject.Find("CoinSpawn").GetComponent<CoinSpawn>();
CoinSpawn test2 = GetComponent<CoinSpawn>();
}
}
}

GameObject.Find("CoinSpawn").GetComponent<CoinSpawn>();
Searches for a GameObject with the name CoinSpawn. Since you told us this component is rather attached to the player object it makes sense that it isn't found.
GetComponent<CoinSpawn>();
searches for a CoinSpawn component on the very same object your CollectingCoin is attached to. From your description this clearly also isn't the case.
Since you say the CoinSpawn is attached to the player then you probably rather want to get the component from
void OnTriggerEnter2D(Collider2D c2d)
{
if (c2d.CompareTag("Player"))
{
...
// rather get the component on the player object you collided with
CoinSpawn test = c2d.GetComponent<CoinSpawn>();
}
}
Alternatively assuming there is only one single instance of CoinSpawn in your scene anyway and not necessarily on your player you could use FindObjectOfType
CoinSpawn test = FindObjectOfType<CoinSpawn>();

First of all, Do not ever use GameObject.Find(), its very expensive as it will go through all game objects in your scene to find the object. and this not a performance wise.
There are many ways to do so.
Easyest one:
Add both script to same gameobject as component.
Make a global variable CoinSpawn inside CollectingCoin script and then use [serializedFiled] tag on top of it, by this way, you can drag and drop the reference in the editor before you start play. and you can access it the way you want.
2nd way:
Is same as first one, but instead of serializedFiled, just cache it at the beginning by using GetComponent.
Just make sure you have both scripts attached to the same gameobject.
public class CollectingCoin : MonoBehaviour
{
UnityEngine.UI.Text Coins;
public static int totalCoins = 0;
CoinSpawn coinSpawn;
private void Start()
{
coinSpawn = GetComponent<CoinSpawn>();
Coins = GameObject.Find("Score").GetComponent<UnityEngine.UI.Text>();
}
void OnTriggerEnter2D(Collider2D c2d)
{
if (c2d.CompareTag("Player"))
{
totalCoins++;
Destroy(gameObject);
Coins.text = "COINS: " + totalCoins.ToString();
// DO Whaterver you want with coinSpawn here
}
}
}

interconnecting scripts in unity3D using the preprocessor [duplicate]

I've searched around and I just can't get this to work. I think I just don't know the proper syntax, or just doesn't quite grasp the context.
I have a BombDrop script that holds a public int. I got this to work with public static, but Someone said that that is a really bad programming habit and that I should learn encapsulation. Here is what I wrote:
BombDrop script:
<!-- language: c# -->
public class BombDrop : MonoBehaviour {
public GameObject BombPrefab;
//Bombs that the player can drop
public int maxBombs = 1;
// Update is called once per frame
void Update () {
if (Input.GetKeyDown(KeyCode.Space)){
if(maxBombs > 0){
DropBomb();
//telling in console current bombs
Debug.Log("maxBombs = " + maxBombs);
}
}
}
void DropBomb(){
// remove one bomb from the current maxBombs
maxBombs -= 1;
// spawn bomb prefab
Vector2 pos = transform.position;
pos.x = Mathf.Round(pos.x);
pos.y = Mathf.Round(pos.y);
Instantiate(BombPrefab, pos, Quaternion.identity);
}
}
So I want the Bomb script that's attached to the prefabgameobject Bombprefab to access the maxBombs integer in BombDrop, so that when the bomb is destroyed it adds + one to maxBombs in BombDrop.
And this is the Bomb script that needs the reference.
public class Bomb : MonoBehaviour {
// Time after which the bomb explodes
float time = 3.0f;
// Explosion Prefab
public GameObject explosion;
BoxCollider2D collider;
private BombDrop BombDropScript;
void Awake (){
BombDropScript = GetComponent<BombDrop> ();
}
void Start () {
collider = gameObject.GetComponent<BoxCollider2D> ();
// Call the Explode function after a few seconds
Invoke("Explode", time);
}
void OnTriggerExit2D(Collider2D other){
collider.isTrigger = false;
}
void Explode() {
// Remove Bomb from game
Destroy(gameObject);
// When bomb is destroyed add 1 to the max
// number of bombs you can drop simultaneously .
BombDropScript.maxBombs += 1;
// Spawn Explosion
Instantiate(explosion,
transform.position,
Quaternion.identity);
In the documentation it says that it should be something like
BombDropScript = otherGameObject.GetComponent<BombDrop>();
But that doesn't work. Maybe I just don't understand the syntax here. Is it suppose to say otherGameObject? Cause that doesn't do anything. I still get the error : "Object reference not set do an instance of an object" on my BombDropScript.maxBombs down in the explode()

You need to find the GameObject that contains the script Component that you plan to get a reference to. Make sure the GameObject is already in the scene, or Find will return null.
GameObject g = GameObject.Find("GameObject Name");
Then you can grab the script:
BombDrop bScript = g.GetComponent<BombDrop>();
Then you can access the variables and functions of the Script.
bScript.foo();
I just realized that I answered a very similar question the other day, check here:
Don't know how to get enemy's health
I'll expand a bit on your question since I already answered it.
What your code is doing is saying "Look within my GameObject for a BombDropScript, most of the time the script won't be attached to the same GameObject.
Also use a setter and getter for maxBombs.
public class BombDrop : MonoBehaviour
{
public void setMaxBombs(int amount)
{
maxBombs += amount;
}
public int getMaxBombs()
{
return maxBombs;
}
}

use it in start instead of awake and dont use Destroy(gameObject); you are destroying your game Object then you want something from it
void Start () {
BombDropScript =gameObject.GetComponent<BombDrop> ();
collider = gameObject.GetComponent<BoxCollider2D> ();
// Call the Explode function after a few seconds
Invoke("Explode", time);
}
void Explode() {
//..
//..
//at last
Destroy(gameObject);
}
if you want to access a script in another gameObject you should assign the game object via inspector and access it like that
public gameObject another;
void Start () {
BombDropScript =another.GetComponent<BombDrop> ();
}

Can Use this :
entBombDropScript.maxBombs += 1;
Before :
Destroy(gameObject);
I just want to say that you can increase the maxBombs value before Destroying the game object. it is necessary because, if you destroy game object first and then increases the value so at that time the reference of your script BombDropScript will be gone and you can not modify the value's in it.

Why am i Getting NullReferenceException when trying to create a HealthPack in Unity C#? [duplicate]

This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 6 years ago.
Ok guys and gals I'm having an issue again with some code. Basically once I start and it attempts to create a Health Pack it's throwing an error that:
NullReferenceException: Object reference not set to an instance of an object
HealthSpawnerScript.Update () (at Assets/Scripts/HealthSpawnerScript.cs:31)
below is the code i'm running. The gameobject PlayerController houses a method used to return Player Health named PlayerHealth(). In awake I set playerController to find the script and method I'm after. Then in update i'm trying to call the method and assign it to a variable for use in the script later. I know this should be simple but i'm having a brain fart guys.
public PlayerController playerController;
private int healthHolder;
void OnAwake()
{
playerController = GameObject.Find ("PlayerHealth").GetComponent<PlayerController> ();
}
// Use this for initialization
void Start ()
{
//set healthExist to false to indicate no health packs exist on game start
healthExist = false;
//playerController = GameObject.Find ("PlayerHealth").GetComponent<PlayerController> ();
}
// Update is called once per frame
void Update ()
{
healthHolder = playerController.PlayerHealth();

There is no Unity callback function named OnAwake. You are likely looking for the Awake function.
If that is fixed and your problem is still there, you have to seperate your code into pieces and find out what's failing.
playerController = GameObject.Find ("PlayerHealth").GetComponent<PlayerController> ();
should be changed to
void Awake()
{
GameObject obj = GameObject.Find("PlayerHealth");
if (obj == null)
{
Debug.Log("Failed to find PlayerHealth GameObject");
return;
}
playerController = obj.GetComponent<PlayerController>();
if (playerController == null)
{
Debug.Log("No PlayerController script is attached to obj");
}
}
So, if GameObject.Find("PlayerHealth") fails, that means there is no GameObject with that name in the scene. Please check the spellings.
If obj.GetComponent<PlayerController>(); fails, there is no script called PlayerController that is attached to the PlayerHealth GameObject. Simplify your problem!

Unity2D C# - Can't destroy an Instantiated object

public class playerAttack : MonoBehaviour {
public bool attacking = false;
public Transform Player;
public Transform swordObject_prefab;
Animator anim;
GameObject clone = null;
// Use this for initialization
void Start () {
anim = GetComponent<Animator> ();
}
// Update is called once per frame
void Update () {
if (!attacking && !anim.GetBool ("isSwimming"))
attackCode ();
if (attacking)
coolDown ();
}
void attackCode(){
if (Input.GetButtonDown ("AttackA")) {
Debug.Log ("ATTACK_A");
anim.SetBool ("isAttackingA", true);
attacking = true;
clone = (GameObject)Instantiate(swordObject_prefab, Player.position, Quaternion.identity);
Destroy(clone);
}
if (Input.GetButtonDown ("AttackB")) {
anim.SetBool ("isAttackingB", true);
}
}
void coolDown(){
if (!anim.GetCurrentAnimatorStateInfo(0).IsName ("SwordSwing")) {
attacking = false;
anim.SetBool ("isAttackingA", false);
}
}
Here's my code.
Im trying to get it so when the player presses a button, he swings a sword spawning at the players location. that all works fine, but when i try to remove the sword I get this error in Unity:
InvalidCastException: Cannot cast from source type to destination type.
playerAttack.attackCode () (at Assets/Scripts/Player/playerAttack.cs:33)
playerAttack.Update () (at Assets/Scripts/Player/playerAttack.cs:22)
Thanks for the advice.
By the way, if anyone knows of a better way to use weapons in Unity2D I will be open to suggestions if this way is a cumbersome way of doing things.

You must instantiate prefabs like this.
PrefabTypeObject obj = (TypeOfPrefab)Instantiate(prefab, position, rotation);
or
PrefabTypeObject obj = Instantiate(prefab, position, rotation) as TypeOfPrefab;
otherwise you will get null object or InvalidCastException like now.
Your solution is`
clone = (GameObject)Instantiate(swordObject_prefab.gameObject, Player.position, Quaternion.identity);

Change this line:
public Transform swordObject_prefab;
To this:
public GameObject swordObject_prefab;
But I'm not sure what instantly destroying an object that has been just created is for... Maybe you want to use a delay?
Destroy(clone, 2f); // Destroy clone 2 seconds from now

Unity FPS Game Error [duplicate]

This question already has answers here:
Bullet Prefab Script
(3 answers)
Closed 8 years ago.
I am getting an error in this script.
UnityEngine does not contain a definition for rigidbody (Lines: 22,24)
public class GunShoot : MonoBehaviour
{
public GameObject BulletPrefab;
public float BulletSpeed;
public int BulletsInClip;
public AudioClip GunshotSound;
void Update () {
if (Input.GetButtonDown("Shoot")){
Shoot();
}
}
void Shoot() {
var bullet = Instantiate(BulletPrefab, transform.Find("BulletSpawn").position, transform.Find("BulletSpawn").rotation);
bullet.rigidbody.AddForce(transform.forward * BulletSpeed);
audio.PlayOneShot(GunshotSound);
BulletsInClip--;
}
}
Please tell me what to edit instead of just editing the script.

Your call to Instantiate() doesn't result in a GameObject. It will return a plain Object. So subsequently you're trying to access the RigidBody - using bullet.rigidbody - which an Object has no knowledge about.
When instantiating therefore perform an explicit cast:
var bullet = (GameObject) Instantiate(BulletPrefab, transform.Find("BulletSpawn").position, transform.Find("BulletSpawn").rotation);
Or even explicitly write GameObject bullet = ... to avoid errors like this. If you do, the compiler will start to complain at the location of the true error if you forget the cast.