Shared Worker and Func

[nealles]

Is there any possibility to add Func as a parameter, smth like

status = await testService.Method1("Hello from main thread", OnCallback);

[LostBeard]

You can send an Action as a parameter right now that can take parameters, but Func is not supported as a parameter at this time.

To clarify: The Action is not actually 'sent', it is stored locally, and a unique ID is generated for it. The ID is sent to the worker which can then send a message back to caller with args to call the action with when it wants the action called. I believe (98%) sure the Action reference is released after the method that was sent the action returns. Action parameter lifetime matches the method called.

[LostBeard]

I'm sure there is a way to do what you want. Can you show me how you would use it if it did work and I can come up with a way do it differently?

[nealles]

I just think of this how I will use it.
But first, I noticed that if Func<string, Task> callback is null, the service shows an error in the browser console and the Method1 does not work.
So, is it possible to not show an exception if the callback is null? Perhaps, I won't use it but I can use a parameter for compatibility.

[nealles]

I tried to use Actions and it works when I call a callback directly from a function where it is as a parameter but when I use PeriodicTimer it does not work.
I modified TestService this way:

 public class TestService : ITestService
 {
     private PeriodicTimer? _timer;
     public async Task Method1(string msg, Action<string[]> callback)
     {

         Console.WriteLine($"Method1 called with message: {msg}");
         //I can run this callback from here
         callback(["it works directly from Method1 but does not work from timer"]);
         _timer = new PeriodicTimer(TimeSpan.FromSeconds(5));
         var task = Method2(msg, callback);
     }

     public async Task Method2(string msg, Action<string[]> callback)
     {
         var i = 0;
         while (await _timer!.WaitForNextTickAsync().ConfigureAwait(false))
         {
             var message = $"\nHello{i++} from shared worker {DateTime.Now}";
             // it shows the message in worker console but it does not run the callback
             Console.WriteLine(message);
             callback([message]);
         }
     }
 }

A demo project where it is reproduced is here:
https://github.com/nealles/SharedWebWorkersFixing/tree/main/BlazorWebApp10
if you are not able to clone the solution or you need some additional info let me know please.

[LostBeard]

Looking at this now. Simply put, you are trying to use a callback that has been already released.

#26 (comment)

Action reference is released after the method that was sent the action returns. Action parameter lifetime matches the method called.

It is working in my modified version of your demo:
https://github.com/LostBeard/BlazorWebAppWebWorekrsIssue26

In my modified version, I keep the called method that owns the callback alive long enough for your PerdiodicTimer to call it a few times

[LostBeard]

    public class TestService : ITestService
    {
        private PeriodicTimer? _timer;
        public async Task Method1(string msg, Action<string[]> callback)
        {

            Console.WriteLine($"Method1 called with message: {msg}");
            callback(["it works directly from Method1 but does not work from timer"]);
            _timer = new PeriodicTimer(TimeSpan.FromSeconds(5));
            var task = Method2(msg, callback);
            await Task.Delay(30000); // <<< This keeps callback valid for 30 seconds. callback is released when Method1 exits
        }

        public async Task Method2(string msg, Action<string[]> callback)
        {
            var i = 0;
            while (await _timer!.WaitForNextTickAsync().ConfigureAwait(false))
            {
                var message = $"\nHello{i++} from shared worker {DateTime.Now}";
                Console.WriteLine(message);
                callback([message]);
            }
        }
    }

[nealles]

I understand about the lifetime but perhaps there is a way to use it somehow or there is a way to control a lifetime of a callback.

It is only a demo example, our app might use a number of timers and each of timers might work for hours.

[nealles]

Perhaps, I can use ActionCallback or some other delegate from your library? I see that ActionCallback is IDisposable, so perhaps I can Dispose it in a component's DisposeAsync for example.

[nealles]

https://github.com/nealles/SharedWebWorkersFixing/tree/main/BlazorWebApp10
I tried using ActionCallback but it does not work at all, I updated my project above. Could you submit it or suggest another one please.

[LostBeard]

I modified it to show 1 way you can do what you ask.

https://github.com/LostBeard/BlazorWebAppWebWorekrsIssue26

[nealles]

I understand what you are trying to say me.
I use sharedWorker.OnMessage now and I can control delegates as much as I want and I thought that I can use Action and control it as much as I want but seems I need to rewrite a code to make it work.
if you would want to redesign Action so they will live a little bit more than a function is running, please let me know :)
So far, I will try this way

[LostBeard]

I honestly wouldn't be terribly hard for me to modify the lifetime behavior of Actions so that they can outlive a method call when desired. I'll take a look and get back to you.

[nealles]

Thanks, it wil be great