Button not set to an instance of an object

Question

I was working on a project of mine and it's pretty simple. It's the same concept of 'roll a ball' game that unity has but I added something to it. One thing that I did that I have trouble with is that I have a button and I want to make it disappear when game starts and to appear when the player wins. So I have something like this:

void Start()
{
    //initialise variables
    body = GetComponent<Rigidbody>();
    pointsCount = 0;
    countText.text = "Count: " + pointsCount.ToString();
    winText.text = "";
    pointsCount = 0;
    GameObject nextLevelButton = GameObject.Find("Button");
    nextLevelButton.SetActive(false);

}

For trigger:

void OnTriggerEnter(Collider collider)
{
    //Trigger for pickups
    if (collider.gameObject.CompareTag("Pickup"))
    {
        collider.gameObject.SetActive(false);
        pointsCount++;
        totalPointsCount++;
        AudioSource audio = GetComponent<AudioSource>();
        audio.PlayOneShot(pickup);
        countText.text = "Count: " + pointsCount.ToString();

        //Check if pickups count is equal to total pickups in level to win
        if (pointsCount == pointsScenario[scenesCounter])
        {
            Win();
        }
    }
}

which calls:

void Win()
{
    winText.text = "You Win!";
    AudioSource audio = GetComponent<AudioSource>();
    audio.PlayOneShot(win);
    GameObject nextLevelButton = GameObject.Find("Button");
    nextLevelButton.SetActive(true);
}

For some reason, when I run it, the SetActive(false); at the start works but when I do it in the win method (or in the trigger method right after or before I call win method) I get an error saying "object reference not set to an instance of an object", which is weird cause it is initialized. And for some reason, I can't use GameObject nextLevelButton = GameObject.Find("Button"); as a global variable cause the button would just appear on screen and never leave.

Answer 1

Find works only for objects that are active in the scene, so it can't find the button when it is not.

You can make a field for the button and store it. For this you can either do the Find in Start or just drag it into the slot in the inspector.

public class TheScript : MonoBehaviour
{
    public GameObject nextLevelButton;

    private void Start()
    {
        nextLevelButton = GameObject.Find("Button");
        nextLevelButton.SetActive(false);
    }
}