Spawning Random Prefab from Object Pool

Unity Engine
,
1

I wrote an object pooling script that’s supposed to set active a random prefab from an object pool active every time the camera moves some random distance to the right. So far, all it does is Instantiate and set the prefabs inactive on awake. I can’t get it to reference or set active anything from the list, and I’m not sure what else to try. I’ve tried multiple things from multiple sources, including the Unity - Scripting API: ObjectPool (unity3d.com), but most object pooling examples online are something like “pool exactly 20 identical bullets” and it’s hard to find something like “spawn random prefab from pool”. I would appreciate any feedback/help.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Pool;
public class EOMovement : MonoBehaviour
{
    //camera distance vars
    private int spawnDistanceGoal;
    private int randomStepNumber;
    //object pooling vars
    private int randomListObject;
    public static ObjectPool<GameObject> SharedInstance;
    public List<GameObject> allObjectPool;
    public int randomObjectPoolNumber;
    public GameObject currentObjectInPool;
    void Awake()
    {   
        for(int i = 0; i < allObjectPool.Count; i++)
        {
        currentObjectInPool = Instantiate(allObjectPool[i]);
        currentObjectInPool.SetActive(false);
        }
    }
    void Start()
    {     
        randomStepNumber = Random.Range(1, 7);
        spawnDistanceGoal = (DistanceTravledDisplay.distanceTravled + randomStepNumber);
        StartCoroutine(Spawn());
    }
    private IEnumerator Spawn()
    {     
        if (DistanceTravledDisplay.distanceTravled >= spawnDistanceGoal)
        {
            Debug.Log("Something should spawn now!");
            randomObjectPoolNumber = Random.Range(0, allObjectPool.Count);
            currentObjectInPool = (allObjectPool[randomObjectPoolNumber]);
            currentObjectInPool.SetActive(true);
            //Pooling and Instantiation code would probably go here
            yield return new WaitForSeconds(2);
            randomStepNumber = Random.Range(1, 7);
            spawnDistanceGoal =  (DistanceTravledDisplay.distanceTravled + randomStepNumber);
            StartCoroutine(Spawn());       
        }
        else
        {
            yield return new WaitForSeconds(2);
            StartCoroutine(Spawn());
        }
    }
}
2

I use this to group collections of Prefab / GameObject assets together:

That lets you shuffle and/or randomize things, and keep a nice handle on related things, such as by making an instance of the above and calling it “TallTrees” or “LargeRocks” or whatever.

Beyond that, as far as timing and when it happens, to debug the code above, try this approach:

What is often happening in these cases is one of the following:

  • the code you think is executing is not actually executing at all
  • the code is executing far EARLIER or LATER than you think
  • the code is executing far LESS OFTEN than you think
  • the code is executing far MORE OFTEN than you think
  • the code is executing on another GameObject than you think it is
  • you’re getting an error or warning and you haven’t noticed it in the console window

To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

  • is this code even running? which parts are running? how often does it run? what order does it run in?
  • what are the values of the variables involved? Are they initialized? Are the values reasonable?
  • are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

If you are running a mobile device you can also view the console output. Google for how on your particular mobile target.

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

You must find a way to get the information you need in order to reason about what the problem is.

1 Like