Prefab Pool

Provides efficient and lazy object pool, designed to use with the prefabs referenced by a component.

Features:

• Convenient API
• Simple and efficient
• Highly configurable
• Test coverage

Why

Unlike Unity's built-in object pool (available since version 2021), this pool aims to minimize the need for configuration and reduce the amount of code required to make it work. It is not a replacement for traditional object pools, where a dedicated pool is allocated per object type, but a solution to a specific problem, where there is a necessity to create a large number of instances of different prefabs.

Installation

Follow the guide by this link to install the package using OpenUPM (recommended).

Or you can add the package to your project via UPM using this Git URL: https://github.com/s-rayleigh/PrefabPool.git

Usage

You can access the pool in either of these ways:

• Use the static methods of the GlobalPrefabPool. They will also create the pool object in the GlobalPrefabPool.Instance property on the first usage.
• Use the GlobalPrefabPool.Instance static property that acts like a Singleton.
• Create an object of the PrefabPool class.
• Use your favorite DI framework to inject the PrefabPool class.

When creating a pool instance, you can also specify the name of the object to use as a parent for instances returned to the pool using the itemsParentName argument of a constructor.

To get an object from the pool, use the Get or TryGet methods. The pool itself is prefab-oriented, so you need to use prefab as an argument referenced by a component (e.g., Transform or any inherited from MonoBehaviour).

To return an object to the pool, use the Release method. You should only return the object to the pool from which it's taken.

If the pool has no available objects, it will create new ones, but you can create them in advance using the Prewarm method. It also keeps track of the number of objects it has created, which you can access using the CountAll, CountInactive, and CountActive methods.

You can also configure the pool per prefab using the Configure method and providing the PoolParameters struct, which allows you to specify the following parameters:

• maxCapacity – the max capacity of the pool (int.MaxValue by default).
• activateOnGet – whether to activate an object when it's taken from the pool (true by default).
• groupReturned – enables grouping returned instances into an object to simplify scene objects hierarchy navigation.
• Actions to perform:
  • onCreate – when an object created by the pool.
  • onGet – when an object taken from the pool.
  • onRelease – when an object returned to the pool.
  • onDestroy – when an object destroyed by the pool.

You can adjust these parameters at any time.

When the pool reaches its max capacity, any returned object will be destroyed, the Get method will fail with an exception, and the TryGet method will return false.

To destroy all the inactive objects in the pool, use the ClearInactive method. You can also specify prefab as an argument to destroy only its instances.

If you want to receive the events in the component through which the prefab is referenced, you can implement these interfaces: IPoolGetHandler, IPoolReleaseHandler, and IPoolDestroyHandler.

Please note that the pool is not thread-safe and is intended to be used on the Unity's main thread.

Examples

class MyComponent : MonoBehaviour, IPoolReleaseHandler
{
    [SerializeField]
    private Renderer rend;

    public void SetMaterial(Material material) => this.rend.sharedMaterial = material;

    public void OnPoolRelease() => this.rend.sharedMaterial = null;
}

class Spawner : MonoBehaviour
{
    [SerializeField]
    private MyComponent prefab;

    [SerializeField]
    private Material mat;
    
    private List<MyComponent> instances = new();

    private void Awake()
    {   
        for(var i = 0; i < 500; i++)
        {
            var instance = GlobalPrefabPool.Get(this.prefab);
            instance.SetMaterial(this.mat);
            this.instances.Add(instance);
        }
    }

    private void OnDestroy()
    {
        foreach(var instance in this.instances) GlobalPrefabPool.Release(instance);
    }
}

Configuration example:

GlobalPrefabPool.Configure(this.prefab, new(
    maxCapacity: 500,
    onGet: obj => Debug.Log($"Object {obj.name} is taken from the pool.")
));

See the tests for more examples.