ObjectPool

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class ObjectPool : MonoBehaviour
{
    [SerializeField]
    private GameObject pooledObject;
    [SerializeField]
    private int poolSize;
    [SerializeField]
    private bool willGrow;

    private Transform poolContainer;

    public int TotalActiveObjects
    {
        get
        {
            int activeObjs = 0;
            for (int i = 0; i < pooledObjects.Count; i++)
            {
                if (pooledObjects[i].activeInHierarchy) { activeObjs++; }
            }
            return activeObjs;
        }
    }

    private List<GameObject> pooledObjects;

    void Awake()
    {
        poolContainer = new GameObject("Pool: " + pooledObject.name).transform;
        poolContainer.transform.parent = transform;

        pooledObjects = new List<GameObject>();
        for (int i = 0; i < poolSize; i++)
        {
            CreateAndAddNewObject();
        }
    }

    public GameObject GetPooledObject()
    {
        for (int i = 0; i < pooledObjects.Count; i++)
        {
            if(pooledObjects[i].activeInHierarchy == false)
            {
                return pooledObjects[i];
            }
        }

        if (willGrow)
        {
            Debug.Log("Added a New Item To Pool: " + transform.name);
            return CreateAndAddNewObject();
        }

        return null;
    }

    private GameObject CreateAndAddNewObject()
    {
        GameObject obj = (GameObject)Instantiate(pooledObject);
        obj.SetActive(false);
        obj.transform.parent = poolContainer.transform;
        obj.transform.localPosition = Vector3.zero;
        obj.transform.localRotation = Quaternion.identity;
        pooledObjects.Add(obj);
        return obj;
    }
}