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.
Related
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
}
}
}
This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 1 year ago.
So my game is a 2D top down movement game and my script does make my enemy attack but it constantly loops the attack animation because I obviously don't know what EXACTLY to put code wise to make the enemy attack when in range of the player to do damage instead of letting him constantly loop. Also i seem to be getting an error when i get close to my enemy as of right now it says
NullReferenceException: Object reference not set to an instance of an object
EnemyCombat.Attack () (at Assets/EnemyCombat.cs:36)
EnemyCombat.Update () (at Assets/EnemyCombat.cs:25)
Also, Here is the EnemyCombat script
enemy attausing System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class EnemyCombat : MonoBehaviour
{
public Animator animator;
public Transform AttackPoint;
public float attackRange = 0.5f;
public LayerMask enemyLayers;
public int attackDamage = 5;
public float attackRate = 2f;
float nextAttackTime = 0f;
// Update is called once per frame
void Update()
{
if (Time.time >= nextAttackTime)
{
Attack();
nextAttackTime = Time.time + 1f / attackRate;
}
}
void Attack()
{
animator.SetTrigger("Attack");
Collider2D[] hitEnemies = Physics2D.OverlapCircleAll(AttackPoint.position, attackRange, enemyLayers);
foreach (Collider2D enemy in hitEnemies)
{
enemy.GetComponent<Enemy>().TakeDamage(attackDamage);
}
}
void OnDrawGizmosSelected()
{
if (AttackPoint == null)
return;
Gizmos.DrawWireSphere(AttackPoint.position, attackRange);
}
}
To fix your endless attack loop:
// Update is called once per frame
void Update()
{
if (attackRate >= nextAttackTime) /* checks that nextAttackTime is less than or equal to the attackRate */
{
Attack();
nextAttackTime = Time.deltaTime * 5f; // adds 5 seconds to nextAttackTime
}
else
{
nextAttackTime -= Time.deltaTime; /* if nextAttackTime is greater than the attackRate, subtract one from nextAttackTime. this only happens once per second because you use Time.deltaTime */
}
}
From that NullReference Error it looks like the major problem you're having is that there is no actual point in the code or in the game hierarchy that you are telling your script which gameObject it is referring to.
Line 36 is trying to retrieve that information with .GetComponent<Enemy()>, so you need to provide that reference.
You could do this in the script fairly easily by creating a public variable that you can drag the enemy gameObject into in your hierarchy in Unity.
Try something like:
public GameObject enemyObject;
This will create a variable in the script visible in the hierarchy when you select the script which you can drag the appropriate gameObject into.
There might need to be some adjustments to it because I can't see the rest of your code, but this seems to be the issue.
Another option would be trying to manually adding it in:
void Start()
{
GameObject enemyObject = gameObject.GetComponent<Enemy>();
}
this is taken from Unity Scripting Documentation
I'm trying to make a script that gives the player a stronger attack when a powerup is walked over. It worked fine with a health increase that I made, but I cannot seem to pin down what I'm doing wrong with this one. I've been at it for the past few days and I'm not getting anywhere. The line giving the error is commented, but it can be rather difficult to see. It's the second to the last line of code:
power.damagePerShot = power.damagePerShot + DamageBoost;
I think that I grasp the nature of the error, but I do not understand why I'm receiving it. If power.damagePerShot is taken from PlayerShootingand then this is referenced to the correct script, I'm not understanding where the null reference is coming from.
The conponent is referenced...
The script being referenced is attached to the object...
using UnityEngine;
public class ShootPowerUp : MonoBehaviour
{
public GameObject pickupEffect;
public PlayerShooting playerShooting;
public int DamageBoost = 100;
private void Update()
{
transform.Rotate(new Vector3(15, 30, 45) * Time.deltaTime);
}
void OnTriggerEnter(Collider other)
{
if (other.CompareTag("Player"))
{
ShootPowerPickup(other);
}
}
void ShootPowerPickup(Collider player)
{
Instantiate(pickupEffect, transform.position, transform.rotation);
PlayerShooting power = player.GetComponent<PlayerShooting>();
power.damagePerShot = power.damagePerShot + DamageBoost; //This line is giving the error.
Destroy(gameObject);
}
}
The component PlayerShooting is not attached to the Player GameObject but one of its child's
Instead use GetComponentInChildren like
PlayerShooting power = player.GetComponentInChildren<PlayerShooting>();
and you should be fine.
I'm pretty new to Unity and I've had a look around for similar problems, but I suck at transferring it over into my program.
Anyway, I basically have a class called Scoring that will keep track of how many enemies there are on the level. I want to pass this value into another class called Bullet_explosive. In this class, it will remove one from that total when an enemy has been hit with the bullet. After it has removed one from the total, I want this value to be passed back into Scoring so that it can be displayed on the screen to the player.
Probably been answered a million times, but I'm sick of not knowing how to implement it into my own program.
Thanks in advance.
Here's the Scoring class:
public class Scoring : MonoBehaviour {
// Create gameobject to store the text object within
public GameObject textObject;
// Holds the text displayed on screen
Text actualText;
// Holds the remaining number of enemies
public static int enemiesRemaining = 12;
// Use this for initialization
void Start ()
{
// Stores the gameobject called EnemiesRemaining
textObject = GameObject.Find ("EnemiesRemaining");
// Gets the text component of that gameobject
actualText = textObject.GetComponent<Text> ();
// Stores what text the display will actually show
actualText.text = "Enemies Remaining: " + enemiesRemaining;
}
// Update is called once per frame
void Update ()
{
// Updates the display
actualText.text = "Enemies Remaining: " + enemiesRemaining;
}
Here's the Bullet_explosive class:
public class Bullet_explosive : MonoBehaviour {
// Lifespan of the bullet
float lifespan = 1.5f;
// Setting up game objects
public GameObject fireEffect;
public GameObject explosion;
public GameObject theGate;
//Passing through the enemies remaining
private static int score;
// Use this for initialization
void Start ()
{
}
// Update is called once per frame
void Update ()
{
score = Scoring.enemiesRemaining;
lifespan -= Time.deltaTime;
// Once the lifespan reaches 0, bullet is destroyed
if (lifespan <= 0)
{
Explode ();
}
}
void OnCollisionEnter(Collision collision)
{
if (collision.gameObject.tag == "Enemy")
{
// Reduces the remaining enemies
score -= 1;
// Checks for no remaining enemies
if (score <= 0)
{
// Removes the gate
Destroy(GameObject.FindWithTag ("Gate"));
}
// Changes the tag of the target hit
collision.gameObject.tag = "Untagged";
// Applies visual effects at the position and rotation of the target
Instantiate (fireEffect, collision.transform.position, Quaternion.identity);
Instantiate (explosion, collision.transform.position, Quaternion.identity);
// Removes bullet and target
Explode();
Destroy (collision.gameObject);
}
}
void Explode()
{
Destroy (gameObject);
}
I find it to be too much effort to have two static fields that mean exactly the same thing. You should only make one field for that and always refer to that same field in the Scoring class.
public class Bullet_explosive : MonoBehaviour {
// Lifespan of the bullet
float lifespan = 1.5f;
// Setting up game objects
public GameObject fireEffect;
public GameObject explosion;
public GameObject theGate;
// Use this for initialization
void Start () { }
// Update is called once per frame
void Update ()
{
/* no "score" updating needed here in Update() */
lifespan -= Time.deltaTime;
// Once the lifespan reaches 0, bullet is destroyed
if (lifespan <= 0)
{
Explode ();
}
}
void OnCollisionEnter(Collision collision)
{
if (collision.gameObject.tag == "Enemy")
{
// Reduces the remaining enemies
//Directly modify that one static field
Scoring.enemiesRemaining -= 1;
// Checks for no remaining enemies
if (Scoring.enemiesRemaining <= 0) //here too
{
// Removes the gate
Destroy(GameObject.FindWithTag ("Gate"));
}
// Changes the tag of the target hit
collision.gameObject.tag = "Untagged";
// Applies visual effects at the position and rotation of the target
Instantiate (fireEffect, collision.transform.position, Quaternion.identity);
Instantiate (explosion, collision.transform.position, Quaternion.identity);
// Removes bullet and target
Explode();
Destroy (collision.gameObject);
}
}
void Explode()
{
Destroy (gameObject);
}
And that should be it.
I'm having a bit of trouble getting the Vector3 wayPointPosition to my other script called Walking and changing it into the Transform target. My troubles lie in the fact that I'm trying to grab this dynamic variable from WayPointPositioner (it changes depending on what object is clicked in the stage and whether the player overlaps with this waypoint) and import and use it in another script.
Below is the code I'm using.
WayPointPositioner
using UnityEngine;
using System.Collections;
public class WayPointPositioner : MonoBehaviour {
public Vector3 wayPointPosition = Vector3.zero;
private bool checkPlayerWaypointCollision;
void Start()
{
}
void OnTriggerStay2D (Collider2D other)
{
// Check if collision is occuring with player character.
if (other.gameObject.name == "Player")
{
checkPlayerWaypointCollision = true;
}
else
{
checkPlayerWaypointCollision = false;
}
}
//Check if object is clicked
void OnMouseDown ()
{
// If its the player, then return a new position for the player to move to for walking
// Else debug that its not so
if (checkPlayerWaypointCollision == false)
{
Debug.Log ("Object not colliding and retrieving position");
Debug.Log (wayPointPosition);
Debug.Log (gameObject.name);
wayPointPosition = new Vector3 (transform.position.x, transform.position.y, 10);
wayPointPosition = Camera.main.ScreenToWorldPoint(wayPointPosition);
}
else
{
Debug.Log ("Object is colliding, no movement needed");
}
}
}
Walking
using UnityEngine;
using System.Collections;
public class Walking : MonoBehaviour {
public Transform target;
public WayPointPositioner wayPointPosition;
public bool walkingAnimation = false;
private Animator anim;
void Awake ()
{
anim = GetComponent<Animator> ();
wayPointPosition = GameObject.FindGameObjectWithTag ("Waypoint").GetComponent<WayPointPositioner> ();
}
void Start ()
{
}
void Update ()
{
Debug.Log ("This is in Walking, WPP =" + wayPointPosition);
}
}
As you can see I'm trying to import the wayPointPosition from the seperate class which is attached to the gameobjects called "Waypoint" (In my current layout those are empty objects with circle colliders to check if they have been clicked). However when I run this, I am not getting my Vector, but I'm getting the name of the last waypoint in the hierarchy (I have currently 6 waypoints which can be clicked) and not a Vector.
I hope someone is able to help me / point out my mistake. I'm still learning C# so I might've made a strange / odd assumption which isn't working.
Kind regards,
Veraduxxz.
It looks like invoking GameObject.FindGameObjectWithTag("Waypoint").GetComponent<WayPointPositioner>(); retrieves a component from the game object which matches the specified tag, as well as a type argument T which derives from MonoBehavior.
Calling this should actually give you an instance of your WayPointPositioner class, which you can then pass to whichever methods you want, and interact with its Vector3 however you would like.