how to CORRECTLY load all assets (using Resources.LoadAll)

Hey,

The assumption is that you have a folder named "Levels" inside some Resources folder in your project, because if you don't then the load call will obviously fail. I put together a script based on those methods of loading you provided and tested them out myself just to make sure they behaved as I excepted.

 using UnityEngine;
 using System.Collections;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 
 public class LoadAllTest : MonoBehaviour
 {
     private void Awake()
     {
         // Method #1: Incorrect casting results in InvalidCastException. ==============================================================
         try
         {
             Debug.Log("Loading with Method #1...");
             GameObject[] loadedObjects = (GameObject[])Resources.LoadAll("GameObjects");
 
             foreach(var go in loadedObjects)
             {
                 Debug.Log(go.name);
             }
         }
         catch(Exception e)
         {
             Debug.Log("Method #1 failed with the following exception: ");
             Debug.Log(e);
         }
 
         // Method #2: Incorrect casting results in array of null objects. ====================================
         try
         {
             Debug.Log("Loading with Method #2...");
             GameObject[] loadedObjects = Resources.LoadAll("GameObjects") as GameObject[];
 
             foreach (var go in loadedObjects)
             {
                 Debug.Log(go.name);
             }
         }
         catch (Exception e)
         {
             Debug.Log("Method #2 failed with the following exception: ");
             Debug.Log(e);
         }
 
         // Method #3: Incorrect casting results in array of null objects. ====================================
         try
         {
             Debug.Log("Loading with Method #3...");
             GameObject[] loadedObjects = Resources.LoadAll("GameObjects", typeof(GameObject)) as GameObject[];
 
             foreach (var go in loadedObjects)
             {
                 Debug.Log(go.name);
             }
         }
         catch (Exception e)
         {
             Debug.Log("Method #3 failed with the following exception: ");
             Debug.Log(e);
         }
 
         // Method #4: Incorrect casting results in InvalidCastException. ====================================
         try
         {
             Debug.Log("Loading with Method #4...");
             GameObject[] loadedObjects = (GameObject[])Resources.LoadAll("GameObjects", typeof(GameObject));
 
             foreach (var go in loadedObjects)
             {
                 Debug.Log(go.name);
             }
         }
         catch (Exception e)
         {
             Debug.Log("Method #4 failed with the following exception: ");
             Debug.Log(e);
         }
 
         // Method #5: DOUBLE KILL! Please don't ever do this. I fear the world may implode. ====================================
         try
         {
             Debug.Log("Loading with Method #5...");
             GameObject[] loadedObjects = (GameObject[])Resources.LoadAll("GameObjects", typeof(GameObject)) as GameObject[];
 
             foreach (var go in loadedObjects)
             {
                 Debug.Log(go.name);
             }
         }
         catch (Exception e)
         {
             Debug.Log("Method #5 failed with the following exception: ");
             Debug.Log(e);
         }
 
         // Proper Method: Casting correctly for expected type of loaded objects results in a valid list of loaded objects. ============
         try
         {
             Debug.Log("Loading with Proper Method...");
 
             // This is the short hand version and requires that you include the "using System.Linq;" at the top of the file.
             var loadedObjects = Resources.LoadAll("GameObjects", typeof(GameObject)).Cast<GameObject>();
             foreach(var go in loadedObjects)
             {
                 Debug.Log(go.name);
             }
 
             // Casts each individual UnityEngine.Object into UnityEngine.GameObject and adds it to an actual list of GameObject type. 
             // This one works too but is the long version.
 
             //var loadedObjects = Resources.LoadAll("GameObjects");
             //List<GameObject> gameObjects = new List<GameObject>();
             //foreach (var loadedObject in loadedObjects)
             //{
             //    gameObjects.Add(loadedObject as GameObject);
             //}
 
             //foreach (GameObject go in gameObjects)
             //{
             //    Debug.Log(go.name);
             //}
         }
         catch (Exception e)
         {
             Debug.Log("Proper Method failed with the following exception: ");
             Debug.Log(e);
         }
 
         // ================================================== THOUGHTS =====================================================
 
         // I would never use this variation because it makes a MASSIVE assumption that all assets inside of the specified folder 
         // are actually GameObjects. If someone down the road places a material (or any non-prefab type) in this folder it will 
         // now cause it to fail loading, because those aren't GameObjects, and it will not be apparent at all.
         Resources.LoadAll("GameObjects");
 
         // This variation is preferred as specifying "typeof(YourType)" ensures only assets of type "YourType" get loaded.
         // This is essential if you are casting the loaded assets into a specified type.
         Resources.LoadAll("GameObjects", typeof(GameObject));
     }
 }