A simple implementation of Game Object pooling mechanism for Unity
This implementation was designed for mainly single scene games which persist throughout the session and only disables the gameObject when PoolManager.Destroy is called. So if you are unloading scenes make sure you manually clear the references in the PoolManager script.
Simply download the PoolManager.cs file into your Unity project and you are good to go.
To instantiate a GameObject with poolmanager simply use PoolManager.Instantiate function instead of the normal Object.Instantiate function.
To destroy a GameObject with poolmanager simply use PoolManager.Destroy function. This simply sets the gameobject to be inactive and will be returned to the pool so it may be reused later.
Make sure all initialization code of the objects to be pooled are written in the OnEnable method and all code for deinitialization are written in OnDisable and NOT in Start and Destroy respectively.
By default the globalPoolsize is set to 20 and can be changed for each GameObjects independently by using the PoolManager.SetPoolSize function or by changing the value of the static int globalPoolSize directly. Similarly a globalNetPoolSize exists which can be used to set the total number of objects in pool including the inactive ones.
To instantiate a GameObject by growing the pool simply use PoolManager.InstantiateGrowing function.If this is not used then the first gameObject which was created in the pool which is currently active will be forcefully reused here.
Information about the GameObject Pool can be accessed by using PoolManager.GetPool function.