Unity3D - Expandable Object Pooler

ObjectPooler.cs

using System.Collections.Generic;
using UnityEngine;

namespace Utils
{
    [System.Serializable]
    public class ObjectPoolItem
    {
        public GameObject objectToPool;
        public int amountToPool;
        public bool shouldExpand;
    }

    public class ObjectPooler : MonoBehaviour
    {
        public static ObjectPooler Instance;
        public List<ObjectPoolItem> itemsToPool;
        public List<GameObject> pooledObjects;
        public GameObject ParentObject;

        public void Awake()
        {
            Instance = this;
        }

        public void Start()
        {
            pooledObjects = new List<GameObject>();
            foreach (ObjectPoolItem item in itemsToPool)
            {
                for (int i = 0; i < item.amountToPool; i++)
                {
                    var obj =  Instantiate(item.objectToPool, ParentObject.transform);
                    obj.SetActive(false);
                    pooledObjects.Add(obj);
                }
            }
        }

        public GameObject GetPooledObject(string tag)
        {
            foreach (var t in pooledObjects)
            {
                if (!t.activeInHierarchy && t.CompareTag(tag))
                {
                    return t;
                }
            }

            foreach (ObjectPoolItem item in itemsToPool)
            {
                if (item.objectToPool.CompareTag(tag))
                {
                    if (item.shouldExpand)
                    {
                        var obj =  Instantiate(item.objectToPool, ParentObject.transform);
                        obj.SetActive(false);
                        pooledObjects.Add(obj);
                        return obj;
                    }
                }
            }

            Debug.LogWarning("Returning null for tag: " + tag);
            return null;
        }
    }
}

Not mine, creds to the Creator.