Unity Object Pool

Usage

• Use the namespace ObjectPool
• Your new prefab reference needs to be of type PoolableGameObject instead of GameObject
• On your Start method, call the Prewarm()function

using UnityEngine;
using ObjectPool;

public class TestObjectPool : MonoBehaviour
{
    public PoolableGameObject cubes;

    void Start()
    {
        cubes.Prewarm();
    }
}

• On unity editor, there is additional information to edit:

• Prefab: The GameObject to be pooled
• AmountToPool: How many GameObjects should be instatiated
• ShouldExpand: Should expand the pool when every instantiated objects are already in use?
• Disposable: Should dispose when the pool is soft flushed?

Retrieving

• Instead of using unity Object.Instantiate static method, switch to ObjectPoolManager.Instance.Retrieve(PooledGameObject)
• PooledGameObject.instance is the now the way to access the created GameObject

void Update()
{
    if (Input.GetKeyUp(KeyCode.Space)) {
        PooledGameObject gameObj = ObjectPoolManager.Instance.Retrieve(cubes);

        gameObj.instance.transform.parent = this.transform;
        gameObj.instance.transform.position = Vector3.zero;
        gameObj.instance.SetActive(true);
    }
}

• There is a second optional parameter to the Retrieve function which creates the objects with a delay self recycle
• This parameter represents the time in seconds

void Update()
{
    if (Input.GetKeyUp(KeyCode.Space)) {
        PooledGameObject gameObj = ObjectPoolManager.Instance.Retrieve(cubes, 2f);

        gameObj.instance.transform.parent = this.transform;
        gameObj.instance.transform.position = Vector3.zero;
        gameObj.instance.SetActive(true);
    }
}

Recycling

• Switch Object.Destroy to ObjectPoolManager.Instance.Recycle(PooledGameObject)

void Update()
{
    if (Input.GetKeyUp(KeyCode.Escape)) {
        ObjectPoolManager.Instance.Recycle(gameObj);
    }
}

• Also, it's possible to delay the recycle using a second parameter, the value is in seconds

void Update()
{
    if (Input.GetKeyUp(KeyCode.Escape)) {
        ObjectPoolManager.Instance.Recycle(gameObj, 1f);
    }
}

Flushing the pool

• Use the method ObjectPoolManager.Instance.DisposePool(); to empty the pool
• Remember that only the objects marked as Disposable will be destroyed
• To hard flush the pool, removing every single object, use a boolean parameter ObjectPoolManager.Instance.DisposePool(true);

IPoolable interface

• Optionally, the prefab script can implement IPoolable interface
• This way, every time it's instance is retrieved or recycled, the methods Retrieve() and Recycle() will be fired respectively.

using UnityEngine;
using ObjectPool;

public class CubeBehaviour : MonoBehaviour, IPoolable
{
    public void Retrieve()
    {
        print("Object Retrieved");
    }

    public void Recycle()
    {
        print("Object Recycled");
    }
}

Managed Update

• When working with a great amount of objects, it's considered a good practice to center each individual Update() into a single behaviour in order to optimize performance
• ObjectPoolManager is also able to concentrate instanced objects updates, just extend IManagedUpdate interface
• It's possible to combine IPoolable and IManagedUpdate interfaces

using UnityEngine;
using ObjectPool;

public class CubeBehaviour : MonoBehaviour, IPoolable, IManagedUpdate
{
    public void Retrieve()
    {
        ObjectPoolManager.Instance.RegisterManagedUpdate(this);
    }

    public void Recycle()
    {
        ObjectPoolManager.Instance.UnregisterManagedUpdate(this);
    }

    public void ManagedUpdate(float deltaTime)
    {
        print(deltaTime);
    }

}