I have issue with Object Pooling in Unity

Question

My Get() function in Object-Pooling keeping on instantiate more objects. I can't find the problem, there's no error. this is the Spawner Class.

public class OPool : MonoBehaviour
{
    public Bullet bulletPrefab;
    public UnityEngine.Pool.ObjectPool<Bullet> _bulletPool;
    public static OPool _OPool;
    public void Start()
    {
        _bulletPool = new UnityEngine.Pool.ObjectPool<Bullet>(createFunc: InstantiatePoolBullet, actionOnGet: GetBulletFromPool,
            actionOnRelease: ReturnBulletToPool,DestroyBullet, true, 15,20);
    }

    public void Update()
    {   
        transform.position = transform.parent.position + new Vector3(0f, 3.5f, 2.5f);
    }

    public Bullet InstantiatePoolBullet()
    {
        Bullet bullet = Instantiate(bulletPrefab, transform);
        bullet.SetPool(_bulletPool);
        return bullet;
    }

    public void GetBulletFromPool(Bullet bullet)
    {
             bullet.transform.position = transform.position;
             bullet.transform.rotation = transform.rotation;             
             bullet.gameObject.SetActive(true);      
    }

    public void ReturnBulletToPool(Bullet bullet)
    {
        bullet.gameObject.SetActive(false);
    }
    public void DestroyBullet(Bullet bullet)
    {
        Destroy(bullet.gameObject);
    }
 
}

and this is my Bullet class

public class Bullet : MonoBehaviour
{
    public float speed;
    private ObjectPool<Bullet> _pool;
    public float _deadtime = 0.7f;
    private float _currentTime;
    private Rigidbody rb;
    public int damage;
    public static Bullet bullet;
    private void Awake()
    {
        rb = GetComponent<Rigidbody>();
        _currentTime = _deadtime;
    }

    private void Start()
    {
        bullet = this;
        ApplyVelocity();
    }

    private void Update()
    {
        if (_currentTime > 0)
        {
            _currentTime -= Time.deltaTime;
        }
        else
        {
            DestroyBullet();
        }
    }

    public void SetPool(ObjectPool<Bullet> pool)
    {
        _pool = pool;
    }

    private void OnEnable()
    {
        ApplyVelocity();
        _currentTime = _deadtime;
    }
    
    private void ApplyVelocity()
    {
        rb.velocity = speed * transform.forward;
    }

    private void DestroyBullet()
    {
        if (_pool != null)
        {
            _pool.Release(this);
        }
        else
        {
            Destroy(gameObject);
        }
    }

and this is where I call the Get function, it's in the Player script.

    void Update()
    {
        if (transform.IsChildOf(RunPlayer.Instance.transform) && RunPlayer.Instance._state == NumState.Running)
        {
            _State = State.Free;

        }
        if (_State == State.Free)
        {
            canShoot = true;
            charAnim.SetBool(Starting, true);
            StartCoroutine(ShootR());
        }
    }
    public enum State
    {
        Idle,
        Free
    }
    public IEnumerator ShootR()
    {
        while (canShoot)
        {
            if (downShootRate)
            {
                yield return new WaitForSeconds(.150f);
            }
            yield return new WaitForSeconds(.145f);
            bulletPool._bulletPool.Get();
        }
    }

I'm just a newbie in coding, thank you for taking you time. any advices for me? I can't find the problem.

I have tried debugging, finding for the solution but it still like that. I expected that I can find the problem why it keeps on instantiate.

Answer 1

You should really take a look at the documentation. You will see that nowhere are they instantiating the objects with GameObject.Instantiate(...) because the object pool's Get() method already creates a new object if needed. Take a close look at their CreatePooledItem() method which is what your InstantiatePoolBullet() is analogous to.

So in your method you have:

public Bullet InstantiatePoolBullet()
    {
        Bullet bullet = Instantiate(bulletPrefab, transform);
        bullet.SetPool(_bulletPool);
        return bullet;
    }

Which I believe will actually instantiate a new bullet every time the object pool does.

There's no need to assume how these things work when there is documentation there to explain it to you, albeit not always the most descriptive. Though in this case it's plenty.

I hope this is helpful.