How do I go about ensuring a unique ID value?

Question

I am using Unity and coding in C#. I have a game object called Enemy, which has a script called EnemyMotor. EnemyMotor has an int called ID. When EnemyMotor starts, I need to find an ID value that is not been using by any other instance of EnemyMotor.

For example: Enemy one spawns; check if an ID value of 1 is not being used. Enemy two spawns; check if an ID value of 1 is being been use. In this case, it is, so I need to find another ID value that is not being used. In this case, it should be 2. Continue with Enemy three, Enemy four and so on.

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How do I go about ensuring a unique ID value?

Answer 1

This is fairly simple. Just have a static int to record the next ID, and increment it by one after you set it. All instances of the script will reference the same static int. When each new instance is created, it will run it's Start() method, set the nextID value as it's own, and ensure that the next nextID value is a value that has not already been used. Providing you only ever increment a value, it will never physically fall back on a previous value.

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static int nextID = 0;
public int iD;

public void Start()
{
    iD = nextID;
    nextID++;
}

Answer 2

IF you are instantiating your Enemies, you could put the "ID" in the name, so that in your Unity Scene Hierarchy you would see something like:

Enemie_1
Enemie_2
Enemie_3

Then your script would check for the existence of an ID's enemie.

int my_check_id = 0;
bool check = false;
GameObject check_game_object;

while(check == false)
{
    my_check_id += 1;

    check_game_object = GameObject.Find("Enemie_" + my_check_id);

    if(check_game_object.name == null)
    {
         //MY CEHCK ID IS NOT CURRENTLY USED.
         check = true;
    }//END IF CHECK_GAME_OBJECT.NAME == NULL
}//END WHILE CHECK == FALSE

This code is untested, and not super efficient. If you need to check more than one property you may want to look at using a Singleton GameControl from the unity tutorials, and store into that and check it. But this should answer your initial question.

Let me know if you have any questions, or would like clarification drop a comment, I'm happy to update my answer!