Baksteen.Async.ModernEvents 0.1.0

Baksteen.Async.ModernEvents

ModernEvents are async capable events that support both sync and async subscribers. This implementation is modeled more or less after David Fowler's suggestion on twitter.

Usage

On the producer side, we have to expose a IModernEvent<TArg> property:

using Baksteen.Async.ModernEvents
...

public class ExampleWithModernEvents
{
    // example event argument record
    public record ClientAddedArgs(string Name);

    // privately declare a concrete ModernEvent field
    private ModernEvent<ClientAddedArgs> _clientAddedEvent = new();

    // publicly only expose the IModernEvent interface
    public IModernEvent<ClientAddedArgs> OnClientAdded { get => _clientAddedEvent; }

    public async Task AddClient(string newClientName)
    {
        // add client to database
        ...

        // notify all (sync & async) subscribers
        await _clientAddedEvent.InvokeAsync(new ClientAddedArgs{ Name = newClientName });
    }
}

On the consumer side, subscribing then looks as follows:

var clientRegistry = new ExampleWithModernEvents();

// sync subscription:
clientRegistry.OnClientAdded.Subscribe(args =>
    Console.WriteLine($"Client {args.Name} was added"));

// async subscription:
clientRegistry.OnClientAdded.Subscribe(async args => {
    Console.WriteLine($"Client {args.Name} was added");
    await Task.CompletedTask; });

The Subscribe() method returns a IDisposable so the consumer can unsubscribe from the event:

var clientRegistry = new ExampleWithModernEvents();

// async subscription:
var subscription = clientRegistry.OnClientAdded.Subscribe(async args => {
    Console.WriteLine($"Client {args.Name} was added");
    await Task.CompletedTask; });

// events will be received here

subscription.Dispose();

// we're no longer subscribed here