Async WebRequest and await in the script where data is needed

My final Goal is to have a Start Screen where i start loading the data.
If the User goes to the next screen, i have to check, if loading data already done (and show a loading indicator if its not done)

At the moment for testing, i start the loading data in the Awake() function in the same Script.

Code (CSharp):

1. using System.Collections.Generic;
2. using System.Threading.Tasks;
3. using UnityEngine;
4.  
5. public class PopulateShelf : MonoBehaviour
6. {
7.     private List<Task> tasks = new List<Task>();
8.  
9.     private void Awake()
10.     {
11.         tasks.Add(LoadingData.LoadData());
12.     }
13.     private void Start()
14.     {
15.         waitOnData().GetAwaiter().GetResult();
16.         //Do Something with the data
17.     }
18.  
19.     private async Task waitOnData()
20.     {
21.         await Task.WhenAll(tasks);
22.     }
23. }
24.  

According to this Video:

with GetAwaiter().GetResult() i can await a async method from a non async method.
And with await.Task.WhenAll(tasks) i try to wait until all data is loaded

My WebRequest (LoadingData.LoadData()) looks like the following:

Code (CSharp):

1.  
2. public class LoadingData : MonoBehaviour
3. {
4.     public static Dictionary<int, BookDTO> Books = new Dictionary<int, BookDTO>();
5.     public static List<CategoryDTO> Categories = new List<CategoryDTO>();
6.     public static async Task LoadData()
7.     {
8.         await LoadCategories();
9.         LoadBooks();
10.         await Task.Yield();
11.     }
12.     public static async Task LoadCategories()
13.     {
14.         UnityWebRequest request = UnityWebRequest.Get(Constants.apiURL + Constants.apiURLCategories);
15.         await Task.Yield();
16.         request.SendWebRequest();
17.         if (request.result == UnityWebRequest.Result.ConnectionError)
18.         {
19.             Debug.Log(request.error);
20.         }
21.         else
22.         {
23.             Categories = JsonConvert.DeserializeObject<List<CategoryDTO>>(request.downloadHandler.text);
24.         }
25.  
26.     }
27.     public static async Task LoadBooks()
28.     {
29.         UnityWebRequest request = UnityWebRequest.Get(Constants.apiURL + Constants.apiURLBooks);
30.         await Task.Yield();
31.         request.SendWebRequest();
32.         if (request.result == UnityWebRequest.Result.ConnectionError)
33.         {
34.             Debug.Log(request.error);
35.         }
36.         else
37.         {
38.             List<BookDTO> books = JsonConvert.DeserializeObject<List<BookDTO>>(request.downloadHandler.text);
39.             books.ForEach(b => Books.Add(b.bookId, b));
40.         }
41.     }
42. }
43.  

I have the feeling that it is quite messy... so for any improvements I am also very grateful

 

Why not just use coroutines? Super-simple to reason about. Your web-get coroutine can accept a delegate that it calls back when the data is ready.

 

Thanks for the answer.
I first try it with coroutines but the video mention above says async/await are 'simpler'...
But anyways, if i try it with coroutines.
Then i would start the coroutine in the await.
But how do i check if the coroutines is finished, when i need the data?

 

Go look at the example code for UnityWebRequest.

 

It's probably late but async/await definitely easier to manage and more flexible. Tarodev has good examples why.
I rewrote a portion of my code to get rid of coroutines and am really happy so far. async/await allowed me to decentralize code and get rid of unnecessary wrappers. Code got a lot cleaner and easier to read.

There are some caveats though:
-ThreadPool is not supported in WebGL as of now. So things like Task.Run() and ThreadPool commands will not work in web builds.
-There are some deeper issues with async/await which you can find in top comment under Tarodev video.

I can also propose to use UniTask instead of Task. It's a nice "wrapper" with great WebGL support, multiple features and clear documentation:
https://github.com/Cysharp/UniTask#getting-started