All prefabs have single instance of MonoBehaviour object?

Unity Engine
1

Hi,
I’m completely new to Unity and game engines in general so it may be a complete newbie question. I have a few years of C# programming behind me though.

I created a cube object in the editor and attached the following script to it:

public class preclick : MonoBehaviour
{

    private GameObject clicked = null;
    private bool rotating = false;
    // Use this for initialization
    void Start()
    {
        Debug.Log("Started.");
    }

    // Update is called once per frame
   void Update()
    {
        if (!rotating)
        {
            //check if the left mouse has been pressed down this frame
            if (Input.GetMouseButtonDown(0))
            {
                if (clicked != null)
                    Debug.Log("GameObject is: " + clicked.name);
                else
                    Debug.Log("GameObject is null");
                //empty RaycastHit object which raycast puts the hit details into
                RaycastHit hit;
                //ray shooting out of the camera from where the mouse is
                Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);

                if (Physics.Raycast(ray, out hit))
                {
                    //print out the name if the raycast hits something
                    clicked = hit.collider.gameObject;
                    rotating = true;
                    Debug.Log(hit.collider.name);
                }
            }
        }
        if (clicked != null)
        {
            clicked.transform.Rotate(Vector3.forward * Time.deltaTime * 100);
        }
    }
}

Basically I want the clicked object to start rotating. That works fine. I then create a prefab from that cube (by dragging it into “Assets”) and delete it from the editor window. I create a new empty gameobject and attach the following script to it:

public class startup : MonoBehaviour {

    public GameObject obj;
	// Use this for initialization
	void Start () {
        Instantiate(obj, new Vector3(0, 0, 0), Quaternion.identity);
        Instantiate(obj, new Vector3(2, 0, 0), Quaternion.identity);
	}
	
	// Update is called once per frame
	void Update () {
	
	}
}

In the editor I drag the cube prefab into obj slot of the empty gameobject. Everything works, I get 2 cubes drawn on screen, side by side. HOWEVER, when I click one it starts rotating, when I click the other one, nothing happens. It seems that the “rotating” variable is already set to true and it doesn’t register the click.
It looks as if there is only one object of class “preclick” between the 2 cubes, is that correct? Shouldn’t each cube have its own instance of the preclick object?
So do I have to keep arrays of my prefab objects in the behaviour script or what is the preffered way of dealing with that?

I searched for answers but couldn’t find anything similiar to my problem. Sorry if it’s obvious :slight_smile:

2

Is it the Cube at (0,0,0) that works? Just for fun, try setting a distance on your raycast and see if that fixes the issue.

e.g.

if (Physics.Raycast(ray, out hit, 50.0f))

EDIT: But to answer the question in general, no - each object is its own instance of the class in this case.

3

No, that doesn’t change anything. The cube that I click first is the rotating one. Both cubes work but only 1 at a time. I can’t make both of them rotate at the same time, as if the rotating boolean is shared between both of them…

4

OK, that was a bit stupid of me… fixed it with:

 if (Physics.Raycast(ray, out hit, 50.0f))
                {
                    //print out the name if the raycast hits something
                    if (hit.collider.gameObject == this.gameObject)
                    {
                        clicked = hit.collider.gameObject;
                        rotating = true;
                        Debug.Log(hit.collider.name);
                    }
                }

I didn’t check if the hit is actually the current object so it set the boolean to true for every object if ANY object was hit by raycast.

Sorry, newbie problems :wink: Thanks for looking into it though :slight_smile:

5

Actually it would be a lot easier if you used OnMouseDown.

–Eric

6

Thanks, you’re right. I’m learning Unity and I just adapted some sample code that used raycast. OnMouseDown works perfectly.