something about the multi-object pooling

Scripting
1

hi,everyone ,i just watched the live archive about the object pooling,and when i wrote it myself and got this question,here is my code piece:

using UnityEngine;
using UnityEngine;
using System.Collections;
using System.Collections.Generic;
public class MyObjectPool : MonoBehaviour {
    public static MyObjectPool current;
    public List<GameObject>    poolObjects;
    public Dictionary<string,List<GameObject>> diffPooledObjects;
    private int poolAmount ;
    void Awake(){
        current = this;
    }
    void Start(){
        poolAmount = 10;
        diffPooledObjects = new Dictionary<string,List<GameObject>>();
        CreatePoolObjects ();
    }
    void CreatePoolObjects(){
        foreach(GameObject poolObj in poolObjects){
            List<GameObject> tempList = new List<GameObject>();
            for(int i = 0; i < poolAmount; i++){
                GameObject tempObj = (GameObject)Instantiate(poolObj);
                tempObj.SetActive(false);
                tempList.Add(tempObj);
            }
           
            diffPooledObjects.Add (poolObj.name,tempList);
        }
    }
    public GameObject GetPooledObject(string name){
        List<GameObject> pooledObjects;
        if(diffPooledObjects.TryGetValue(name,out pooledObjects)){
            for(int i = 0;  i < pooledObjects.Count; i++){
                if(!pooledObjects[i].activeInHierarchy){
                    return pooledObjects[i];
                }
            }
            GameObject tempObj = (GameObject)Instantiate(pooledObjects[0]);
            tempObj.SetActive(false);
            pooledObjects.Add(tempObj);
            return tempObj;
        }else{
            return null;
        }
    }
 
}

im doing the infinite runner game llike the live archive said
1.i have three types of gameobject to be pooled:small ground,midium ground and large ground,

2.In Unity inspector,i put the references of these ground prefabs to the List “poolObjects”

3.The Dictionary<string,List> means that each List is a object pool,derminated by object name

4.In the CreatePoolObjects() ,i just intialize all the object pools,

5…In GetPooledObject(string name),i want to get object from different object pools by string

here is the exception:
NullReferenceException: Object reference not set to an instance of an object
MyObjectPool.GetPooledObject (System.String name) (at Assets/Scripts/ObjectPool/MyObjectPool.cs:31),
accur at " if(diffPooledObjects.TryGetValue(name,out pooledObjects)){"

2

It could be a lot of things, but a good place to start might be to put the instantiation of diffPooledObjects into ‘Awake’. You are instantiating it in Start, which means that there might be a script out there that is calling the GetPooledObject function before your MyObjectPool has its own Start function called.

To be extra safe you can just instantiate it on the same line that you declare it, this way you can be sure that diffPooledObjects will not be null when you try to access it for the first time.

    public Dictionary<string,List<GameObject>> diffPooledObjects = new Dictionary<string,List<GameObject>>();
3

OH YEAH!! it works~ i really appreciate it!!! thanks anyway~:smile::smile:

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