Destroy all previous clones.

Questions & Answers
1

I want only one prefab to be in the scene at once. Each time I make a new one ingame, I want the previous one to be destroyed. How do I get it to check the number of clones in the scene, and only keep the one that was created sooner?

2

I think this would work. I wrote it so you can have x many clones and if you have one more the first one get's destroyed. In your case this maximum number is one.

var maxNumberOfClones : int;

var location : Vector3;
var prefab : GameObject;

private var numberOfClose : int;
private var activeClones : Array = new Array ();

function Update () {

    if (some_condition) { //when do you want to instantiate

        activeClones.Add(Instantiate(prefab,location,Quaternion.identity); //at the end of the array, add the newest clone

        if(activeClones.length > maxNumberOfClones) { //if there are now to many clones

            Destroy(activeClones[0]) //destroy the first entry of the array

            activeClones.Shift(); // remove this entry from the array    
        }

    }

}
3

Keep a reference to the clone when you instantiate it.

var prefab : GameObject;
private var clone : GameObject;

function Spawn () {
    if (clone) {
        Destroy(clone);
    }
    clone = Instantiate(prefab);
}