Maui dependency injection

Question

@Leon Lu (Shanghai Wicresoft Co,.Ltd.) I try to use the new dependency service in my app, but I broke it

Now is not calling the method to download the word.

Look

Maui Program

  public static MauiApp CreateMauiApp()  
    {  
        var builder = MauiApp.CreateBuilder();  
        builder.UseMauiApp<App>().ConfigureFonts(fonts =>  
        {  
            fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");  
            fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");  
        });  
  
        builder.Services.AddSingleton<WordService>();  
        builder.Services.AddSingleton<MainPageViewModel>();  
        builder.Services.AddSingleton<MainPage>();  
        builder.Services.AddSingleton<IGetWord, WordService>();  
        return builder.Build();  
    }  

IGetWord

public interface IGetWord  
{  
    Task<string> DownloadRandomWordAsync();  
}  

Serrvice, here is where I implemented the interface

public class WordService : IGetWord  
{  
    readonly HttpClient client;  
  
    public WordService()  
    {  
        client = new HttpClient();  
    }  
  
    public async Task<string> DownloadRandomWordAsync()  
    {  
        var url = "https://random-words-api.vercel.app/word/";  
  
        var response = await client.GetAsync(url);  
  
        if (response.IsSuccessStatusCode)  
        {  
            var json = await response.Content.ReadFromJsonAsync<List<WordClass>>();  
  
            return json.FirstOrDefault().word;  
        }  
  
        return null;  
    }  
}  

And Finally my VM

public partial class MainPageViewModel : ObservableObject  
{  
    readonly IGetWord getWord;  
  
    string answer = string.Empty;  
    readonly List<char> charList = new();  
  
    [ObservableProperty]  
    private string _spotlight;  
  
  
    public MainPageViewModel(IGetWord getWord)  
    {  
        this.getWord = getWord;  
    }  
  
    private async Task<string> GetWord()  
    {  
        answer = await getWord.DownloadRandomWordAsync();  
        return answer;  
    }  
  
    private void CalculateWord(string ans, List<char> guessed)  
    {  
        var temp = ans.Select(x => guessed.IndexOf(x) >= 0 ? x : '_').ToArray();  
        Spotlight = string.Join(' ', temp);  
    }  
  
    public async Task InitializeAsync()  
    {  
        answer = await GetWord();  
        CalculateWord(answer, charList);  
    }  
  
}  

Answer 1

Hello,

I tried o call it it the constructor, but my app frezes

You cannot call await/async method in the constructor
You can refer to The Asynchronous Initialization Pattern.

1. Create a IAsyncInitialization interface public interface IAsyncInitialization
   {
   Task InitializeAsync();
   }
   2. Then implement this interface and initialize this InitializeAsync() in your MainPageViewModel constructor(Note: do not forget to add public Task Initialization { get; private set; }). public partial class MainPageViewModel : ObservableObject, IAsyncInitialization
      {
      readonly IGetWord getWord;
      string answer = string.Empty;
      // I add characters for tesing.
      readonly List<char> charList = new() { 'j', 'a', 'c' }; [ObservableProperty]
      private string _spotlight; public MainPageViewModel(IGetWord getWord)
      {
      this.getWord = getWord;
      //initialize this InitializeAsync()
      Initialization = InitializeAsync(); }
      public Task Initialization { get; private set; } private void CalculateWord(string ans, List<char> guessed)
      {
      var temp = ans.Select(x => guessed.IndexOf(x) >= 0 ? x : '_').ToArray();
      Spotlight = string.Join(' ', temp);
      }
      private async Task<string> GetWord()
      {
      answer = await getWord.DownloadRandomWordAsync();
      return answer;
      }
      public async Task InitializeAsync()
      {
      answer = await GetWord();
      CalculateWord(answer, charList);
      }
      }

Best Regards,

Leon Lu

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Answer 2

Is InitializeAsync being called anywhere?