Change variables of an instantiated prefab from another script.

So I’ve recently started learning C# through school and thought game development would be a fun side hobby. I started with a simple flappy bird tutorial on Youtube made by “Game Maker’s Toolkit” and when i was done i wanted to implement a feature of my own. In his tutorial, when you die and sit in the game over screen, the pipes keep spawning and moving in the background so i wanted to try to get the pipes to stop when you die since the reasons the pipes are moving is to simulate the bird moving. After 2 days of head scratching, reading forums and different unity documentation, coding and then some more head scratching i cant seem to figure out how to do this.

I have a script on a empty game object that spawns prefabs of the pipes and then a script inside the prefab that makes them move. I also have a script on another empty game object that handles a game over screen when u die, what i want to do is change the move speed of the pipes to “0” from the game over script and also change so it doesn’t spawn more pipes. I’ve succeeded in stopping more pipes from spawning but the ones already spawned keep moving since it doesn’t seem like i can change a prefabs scripts variables from another script?

I’ll put all the scripts i have down below and maybe some of u can point me in the right direction

Bird script

using UnityEngine;

public class BirdScript : MonoBehaviour
{
    public Rigidbody2D myRigidbody;
    public float flapStrength;
    public LogicScript logic;
    public bool birdIsAlive = true;

    // Start is called before the first frame update
    void Start()
    {
        logic = GameObject.FindGameObjectWithTag("Logic").GetComponent<LogicScript>();
    }

    // Update is called once per frame
    void Update()
    {
        if (Input.GetKeyDown(KeyCode.Space) == true && birdIsAlive == true)
        {
            myRigidbody.velocity = Vector2.up * flapStrength;
        }
        if (transform.position.y < -60 || transform.position.y > 60)
        {
            logic.gameOver();
        }
    }
    private void OnCollisionEnter2D(Collision2D collision)
    {
        logic.gameOver();
        birdIsAlive = false;
    }
}

PipeMoveScript

using UnityEditor;
using UnityEngine;

public class PipeMoveScript : MonoBehaviour
{
    public float moveSpeed = 5;
    public float deadZone = -45;
    public LogicScript logic;

    // Start is called before the first frame update
    void Start()
    {

    }

    // Update is called once per frame
    void Update()
    {
        transform.position = transform.position + (Vector3.left * moveSpeed) * Time.deltaTime;

        if (transform.position.x < deadZone)
        {
            Destroy(gameObject);
        }
    }
}

PipeSpawnerScript

using UnityEngine;

public class PipeSpawnerScript : MonoBehaviour
{
    public GameObject pipe;
    public float SpawnRate = 3;
    private float timer = 0;
    public float pipeOffset = 10;
    public bool spawning = true;

    // Start is called before the first frame update
    void Start()
    {
        SpawnPipe();
    }

    // Update is called once per frame
    void Update()
    {
        if (timer < SpawnRate || spawning == false)
        {
            timer += Time.deltaTime;
        }
        else
        {
            SpawnPipe();
            timer = 0;

        }
    }

    void SpawnPipe()
    {
        float lowestPoint = transform.position.y - pipeOffset;
        float highestPoint = transform.position.y + pipeOffset;
        Instantiate(pipe, new Vector3(transform.position.x, Random.Range(lowestPoint, highestPoint), 0), transform.rotation);
    }
}

Logic Script

using UnityEditor;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;

public class LogicScript : MonoBehaviour
{
    public int playerScore;
    public Text scoreText;
    public GameObject gameOverScreen;
    public PipeSpawnerScript spawn;
    public PipeMoveScript move;

    void Start()
    {
        spawn = GameObject.FindGameObjectWithTag("Stop Pipe").GetComponent<PipeSpawnerScript>();
        move = GameObject.FindGameObjectWithTag("Stop Pipe").GetComponent<PipeMoveScript>();
    }
    [ContextMenu("Increase Score")]
    public void addScore()
    {
        playerScore = playerScore + 1;
        scoreText.text = playerScore.ToString();
    }

    [ContextMenu("Decrease Score")]
    public void removeScore()
    {
        playerScore = playerScore - 1;
        scoreText.text = playerScore.ToString();
    }

    public void restartGame()
    {
        SceneManager.LoadScene(SceneManager.GetActiveScene().name);
    }

    public void gameOver()
    {
        gameOverScreen.SetActive(true);
        spawn.spawning = false;
        move.moveSpeed = 0;
    }

PipeMiddleScript

using UnityEngine;

public class PipeMiddleScript : MonoBehaviour
{
    public LogicScript logic;
    // Start is called before the first frame update
    void Start()
    {
        logic = GameObject.FindGameObjectWithTag("Logic").GetComponent<LogicScript>();
    }

    // Update is called once per frame
    void Update()
    {

    }

    private void OnTriggerEnter2D(Collider2D collision)
    {
        if (collision.gameObject.layer == 3)
        {
            logic.addScore();
        }
    }
}

Time to start debugging! Here is how you can begin your exciting new debugging adventures:

You must find a way to get the information you need in order to reason about what the problem is.

Once you understand what the problem is, you may begin to reason about a solution to the problem.

What is often happening in these cases is one of the following:

  • the code you think is executing is not actually executing at all
  • the code is executing far EARLIER or LATER than you think
  • the code is executing far LESS OFTEN than you think
  • the code is executing far MORE OFTEN than you think
  • the code is executing on another GameObject than you think it is
  • you’re getting an error or warning and you haven’t noticed it in the console window

To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

  • is this code even running? which parts are running? how often does it run? what order does it run in?
  • what are the names of the GameObjects or Components involved?
  • what are the values of the variables involved? Are they initialized? Are the values reasonable?
  • are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

You can also supply a second argument to Debug.Log() and when you click the message, it will highlight the object in scene, such as Debug.Log("Problem!",this);

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

Visit Google for how to see console output from builds. If you are running a mobile device you can also view the console output. Google for how on your particular mobile target, such as this answer for iOS: https://discussions.unity.com/t/700551 or this answer for Android: https://discussions.unity.com/t/699654

If you are working in VR, it might be useful to make your on onscreen log output, or integrate one from the asset store, so you can see what is happening as you operate your software.

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

If your problem is with OnCollision-type functions, print the name of what is passed in!

Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

https://discussions.unity.com/t/839300/3

“When in doubt, print it out!™” - Kurt Dekker (and many others)

Note: the print() function is an alias for Debug.Log() provided by the MonoBehaviour class.

Thank you Kurt, that was actually really helpful! I found out that even though the code ran it didn’t change the value like i wanted it to do. I instead made the pipe movement dependent on the bird being alive and got the feature i was looking for. Much appreciated! :slight_smile: