OneShotOneKill/Assets/Script/InGame/Projectile/ProjectileMgr.cs

using System.Collections.Generic;
using UnityEngine;

public class ProjectileMgr : MonoBehaviourSingletonTemplate<ProjectileMgr>
{
    [Header("Pool Setting")]
    public Transform tf_parent;
    public Projectile projectilePrefab;
    public int poolSize = 50;

    Queue<Projectile> pool = new Queue<Projectile>();

    protected override void Awake()
    {
        base.Awake();
        InitPool();
    }

    void InitPool()
    {
        for (int i = 0; i < poolSize; i++)
        {
            Projectile p = CreateExtra();
            p.gameObject.SetActive(false);
            pool.Enqueue(p);
        }
    }

    public Projectile Get()
    {
        Projectile p = pool.Count > 0 ? pool.Dequeue() : CreateExtra();
        p.gameObject.SetActive(true);
        return p;
    }

    public void Return(Projectile p)
    {
        p.gameObject.SetActive(false);
        pool.Enqueue(p);
    }

    Projectile CreateExtra()
    {
        Projectile p = Instantiate(projectilePrefab, tf_parent);
        p.SetOwner(this);
        return p;
    }
}