Version: 2022.3
  • C#


class in UnityEngine.Pool


Implemented in:UnityEngine.CoreModule

Implements interfaces:IObjectPool<T0>

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A stack based IObjectPool<T0>.

Object Pooling is a way to optimize your projects and lower the burden that is placed on the CPU when having to rapidly create and destroy new objects. It is a good practice and design pattern to keep in mind to help relieve the processing power of the CPU to handle more important tasks and not become inundated by repetitive create and destroy calls. The ObjectPool uses a stack to hold a collection of object instances for reuse and is not thread-safe.

using System.Text;
using UnityEngine;
using UnityEngine.Pool;

// This component returns the particle system to the pool when the OnParticleSystemStopped event is received. [RequireComponent(typeof(ParticleSystem))] public class ReturnToPool : MonoBehaviour { public ParticleSystem system; public IObjectPool<ParticleSystem> pool;

void Start() { system = GetComponent<ParticleSystem>(); var main = system.main; main.stopAction = ParticleSystemStopAction.Callback; }

void OnParticleSystemStopped() { // Return to the pool pool.Release(system); } }

// This example spans a random number of ParticleSystems using a pool so that old systems can be reused. public class PoolExample : MonoBehaviour { public enum PoolType { Stack, LinkedList }

public PoolType poolType;

// Collection checks will throw errors if we try to release an item that is already in the pool. public bool collectionChecks = true; public int maxPoolSize = 10;

IObjectPool<ParticleSystem> m_Pool;

public IObjectPool<ParticleSystem> Pool { get { if (m_Pool == null) { if (poolType == PoolType.Stack) m_Pool = new ObjectPool<ParticleSystem>(CreatePooledItem, OnTakeFromPool, OnReturnedToPool, OnDestroyPoolObject, collectionChecks, 10, maxPoolSize); else m_Pool = new LinkedPool<ParticleSystem>(CreatePooledItem, OnTakeFromPool, OnReturnedToPool, OnDestroyPoolObject, collectionChecks, maxPoolSize); } return m_Pool; } }

ParticleSystem CreatePooledItem() { var go = new GameObject("Pooled Particle System"); var ps = go.AddComponent<ParticleSystem>(); ps.Stop(true, ParticleSystemStopBehavior.StopEmittingAndClear);

var main = ps.main; main.duration = 1; main.startLifetime = 1; main.loop = false;

// This is used to return ParticleSystems to the pool when they have stopped. var returnToPool = go.AddComponent<ReturnToPool>(); returnToPool.pool = Pool;

return ps; }

// Called when an item is returned to the pool using Release void OnReturnedToPool(ParticleSystem system) { system.gameObject.SetActive(false); }

// Called when an item is taken from the pool using Get void OnTakeFromPool(ParticleSystem system) { system.gameObject.SetActive(true); }

// If the pool capacity is reached then any items returned will be destroyed. // We can control what the destroy behavior does, here we destroy the GameObject. void OnDestroyPoolObject(ParticleSystem system) { Destroy(system.gameObject); }

void OnGUI() { GUILayout.Label("Pool size: " + Pool.CountInactive); if (GUILayout.Button("Create Particles")) { var amount = Random.Range(1, 10); for (int i = 0; i < amount; ++i) { var ps = Pool.Get(); ps.transform.position = Random.insideUnitSphere * 10; ps.Play(); } } } }


CountActiveNumber of objects that have been created by the pool but are currently in use and have not yet been returned.
CountAllThe total number of active and inactive objects.
CountInactiveNumber of objects that are currently available in the pool.


ObjectPool_1Creates a new ObjectPool instance.

Public Methods

ClearRemoves all pooled items. If the pool contains a destroy callback then it will be called for each item that is in the pool.
DisposeRemoves all pooled items. If the pool contains a destroy callback then it will be called for each item that is in the pool.
GetGet an instance from the pool. If the pool is empty then a new instance will be created.
ReleaseReturns the instance back to the pool. Returning an instance to a pool that is full will cause the instance to be destroyed.