What is the correct way to subscribe to ReactiveCommand in RxUI 6?

Question

I am trying to get a simple skeleton ViewModel set up with ReactiveUI 6 (beta) and keep getting compiler errors (in Xamarin Studio, FWIW).

Code:

using System;
using System.Reactive;
using System.Reactive.Linq;
using ReactiveUI;

// ...

public IReactiveCommand TryAuthenticateCommand { get; protected set; }

// ...

this.TryAuthenticateCommand = ReactiveCommand.Create(
this.WhenAny(
    x => x.Username,
    x => x.Password,
    (username, password) => 
        !string.IsNullOrWhiteSpace(username.Value) && 
        !string.IsNullOrWhiteSpace(password.Value)));
this.TryAuthenticateCommand.Subscribe(x => MessageBus.Current.SendMessage("Yes!"));

Error:

Error CS0411: The type arguments for method `System.ObservableExtensions.Subscribe<T>(this System.IObservable<T>, System.Action<T>)' cannot be inferred from the usage. Try specifying the type arguments explicitly (CS0411)

Ana Betts · Accepted Answer · 2014-04-24T19:00:59.647

2

This code is perfect, i think you're just missing a using statement, "using System.Reactive"

Update: The reason that this doesn't work is code that's not in the snippet. You declared TryAuthenticateCommand as IReactiveCommand which doesn't implement IObservable<T> (what would T be?).

In this case, since you're not providing an async method to go along with it, ReactiveCommand returns you the CommandParameter, which is an object. So declare it as ReactiveCommand<object> and everything works

edited Apr 24 '14 at 19:00

answered Apr 24 '14 at 16:38

Ana Betts

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Tried adding `using System.Reactive;` and it made no difference. – Michael Teper Apr 24 '14 at 17:00
System.Reactive.Linq? I can never remember where that extension method lives – Ana Betts Apr 24 '14 at 17:01
Yup, I've got them both (see updated question). Any others? :) – Michael Teper Apr 24 '14 at 17:10
Can you send me a small repro project? paul@paulbetts.org – Ana Betts Apr 24 '14 at 18:10
Thanks, that makes sense. So what should the prototypical definition look like? – Michael Teper Apr 24 '14 at 18:57
RE: "since you are not providing an async method", could you give an example? Want to make sure I understand the correct usage pattern. Thanks! – Michael Teper Apr 24 '14 at 19:05
You're using it correctly here, but if you *also* wanted to tie this method to some sort of async method (via the "execute" parameter), the "T" would be the result of the async method instead (way more convenient!) – Ana Betts Apr 24 '14 at 19:06

What is the correct way to subscribe to ReactiveCommand in RxUI 6?

1 Answers1