unity3d Object Pooling Simple object pool
Example
Below is an example of an object pool that allows renting and returning of a given object type. To create the object pool a Func for the create function and an Action to destroy the object are required to give the user flexibility. On requesting an object when the pool is empty a new object will be created and on requesting when the pool has objects then objects are removed from the pool and returned.
Object Pool
public class ResourcePool<T> where T : class
{
private readonly List<T> objectPool = new List<T>();
private readonly Action<T> cleanUpAction;
private readonly Func<T> createAction;
public ResourcePool(Action<T> cleanUpAction, Func<T> createAction)
{
this.cleanUpAction = cleanUpAction;
this.createAction = createAction;
}
public void Return(T resource)
{
this.objectPool.Add(resource);
}
private void PurgeSingleResource()
{
var resource = this.Rent();
this.cleanUpAction(resource);
}
public void TrimResourcesBy(int count)
{
count = Math.Min(count, this.objectPool.Count);
for (int i = 0; i < count; i++)
{
this.PurgeSingleResource();
}
}
public T Rent()
{
int count = this.objectPool.Count;
if (count == 0)
{
Debug.Log("Creating new object.");
return this.createAction();
}
else
{
Debug.Log("Retrieving existing object.");
T resource = this.objectPool[count-1];
this.objectPool.RemoveAt(count-1);
return resource;
}
}
}
Sample usage
public class Test : MonoBehaviour
{
private ResourcePool<GameObject> objectPool;
[SerializeField]
private GameObject enemyPrefab;
void Start()
{
this.objectPool = new ResourcePool<GameObject>(Destroy,() => Instantiate(this.enemyPrefab) );
}
void Update()
{
// To get existing object or create new from pool
var newEnemy = this.objectPool.Rent();
// To return object to pool
this.objectPool.Return(newEnemy);
// In this example the message 'Creating new object' should only be seen on the frame call
// after that the same object in the pool will be returned.
}
}
