How to find out the number of child object of an instantiated prefab in Unity?

Question

I have 2 objects:

• Tile: Just a single rectangular plane
• Stripe: A collection of tiles

In the GameManager script I'm instantiating a stripe every 2 seconds, and in the Stripe script I'm instantiating Tiles using for loop with a random number and I'm parenting them to the stripe just created.

My problem is that I want to find out the number the of tiles per instantiated Stripe?

I mean using newStripe.transform.childCount won't work because it will always return zero, and just for testing reasons I edited the Stripe prefab by adding an empty gameobject and then applied the changes newStripe.transform.childCount will return 1.

I know that I'm supposed to use object pooling techniques in such situations, but I'm a beginner and I'm trying to learn.

// GameManager Script

void Update()
{
    timeBetweenSpawns -= Time.deltaTime;

    if (timeBetweenSpawns < -2)
    {           
       Stripe newStripe = Instantiate(stripePrefab, spawnPosition, 
       Quaternion.identity);

        // This variable (tilesCountIntStripe) always returns zero
        tilesCountInStripe = newStripe.transform.childCount;

        timeBetweenSpawns = 0;
    }
}

// Stripe Script
void Update()
{
    if (createTile)
    {
        int randomStripesCount = Random.Range(1, 10);
        for (int i = 0; i < randomStripesCount; i++)
        {
            Tile newTile = Instantiate(tile);
            newTile.transform.SetParent(transform, true);
            newTile.transform.localPosition = new Vector2(transform.position.x, (-i * (1.1f)));
            tilesCount += 1;
        }
        createTile = false;
    }
}

Answer 1

It returns 0 where you're asking because Tile::Update() hasn't run yet

If you want that code to run immediately, I suggest doing something like this:

// GameManager Script

void Update()
{
    timeBetweenSpawns -= Time.deltaTime;

    if (timeBetweenSpawns < -2)
    {           
       Stripe newStripe = Instantiate(stripePrefab, spawnPosition, 
         Quaternion.identity);

       tilesCountInStripe = newStripe.GetComponent<Stripe>().Init();
       //Or whatever the exact name of your class is ^ here

       timeBetweenSpawns = 0;
    }
}

// Stripe Script
public int Init()
{
    int randomStripesCount = Random.Range(1, 10);
    for (int i = 0; i < randomStripesCount; i++)
    {
        Tile newTile = Instantiate(tile);
        newTile.transform.SetParent(transform, true);
        newTile.transform.localPosition = new Vector2(transform.position.x, (-i * (1.1f)));
        tilesCount += 1;
    }
    return randomStripesCount;
}

Changes:

1. Rather than waiting for Update to create the tiles, we instantiate them in an Init function that is called from code that you control.
   • This also removes the neccessity of having a createTile field that prevents the update code (which runs once a frame) from running every frame.
     • this should have been a clue that you were doing things in the wrong place
2. Returning the random number of tiles from this Init method (FAST), avoiding having to query the transform hierarchy (SLOW).