ReactiveCommand, MessageBus

[Chris Dickerson]

I am having trouble with ReactiveCommand, attaching it to a button and showing a response.

 

MessageBus - from what I can tell, you have to register, listen/send. Whether I give a name for the contract or not... nothing's working.  My goal is simply to create a message that can be subscribed to by any other view and a message can be sent to the listener(s). Or is the MessageBus something entirely different?  I found that IReactiveCommand is an acceptable source for the registration but... not sure how to bind it to a button and use it to send messages?

 

• RegisterMessageSource(IObservable source) – Register an IObservable as a message source – anything that is published on the IObservable gets published to the bus.
• SendMessage(message) – Publish a single item on the bus instead of having to use an Observable.
• IObservable Listen() – Get an Observable for the specified source – you can either Subscribe to it directly, or use any of the Rx operators to filter what you want.

 

The few examples I can find, have very simple solutions, usually a Console.WriteLine printing out some value.  When I try to use a method in it's place -- no dice.

 

Admittedly I don't have as firm a grasp on LINQ or anonymous methods when it comes to these examples...

 

http://rxwiki.wikidot.com/101samples

 

var cmd = new ReactiveCommand(_ => true, Console.WriteLine);
cmd.CanExecute(null);
>> true

 

cmd.Execute("Hello");
"Hello"

I was able to implement ICommand via a separate class.  I suppose I was under the impression that you could do this with ReactiveCommand without requiring a separate class file.

[Paul Betts]

Hi Chris,

To make a command invoked when a message comes in:

MessageBus.Current.Listen<FooType>().InvokeCommand(myCoolCommand);

which is shorthand for

var myCoolCommand = new ReactiveCommand();

MessageBus.Current.Listen<FooType>()
.Subscribe(x => {
if (!myCoolCommand.CanExecute(x)) return;
myCoolCommand.Execute(x);
});

To *send* a message when a command is invoked, it'd be:

var myCoolCommand = new ReactiveCommand();
MessageBus.Current.RegisterMessageSource(
myCoolCommand.Select(_ => someDataIWantToPassAlong));

Let me know if these examples make no sense and I can explain them :)

--
Paul Betts <pa...@paulbetts.org>

On Tue, May 21, 2013 at 11:50:04AM -0700, Chris Dickerson wrote:
> I am having trouble with *ReactiveCommand*, attaching it to a button and
> showing a response.
>
> *MessageBus* - from what I can tell, you have to register, listen/send.

> Whether I give a name for the contract or not... nothing's working. My
> goal is simply to create a message that can be subscribed to by any other

> view and a message can be sent to the listener(s). Or is the *MessageBus*something entirely different? I found that
> *IReactiveCommand* is an acceptable source for the registration but... not

> sure how to bind it to a button and use it to send messages?
>

> *RegisterMessageSource(IObservable source)* – Register an IObservable as a

> message source – anything that is published on the IObservable gets
> published to the bus.

> *SendMessage(message)* – Publish a single item on the bus instead of having
> to use an Observable.
> *IObservable Listen()* – Get an Observable for the specified source – you

> can either Subscribe to it directly, or use any of the Rx operators to
> filter what you want.
>
> The few examples I can find, have very simple solutions, usually a
> Console.WriteLine printing out some value. When I try to use a method in
> it's place -- no dice.
>
> Admittedly I don't have as firm a grasp on LINQ or anonymous methods when
> it comes to these examples...
>
> http://rxwiki.wikidot.com/101samples
>

> *var* cmd = new *ReactiveCommand*(_ => true, Console.WriteLine);
> cmd.CanExecute(*null*);
> >> *true*

>
>
>
> cmd.Execute("Hello");
> "Hello"
>
> I was able to implement ICommand via a separate class. I suppose I was
> under the impression that you could do this with ReactiveCommand without
> requiring a separate class file.
>

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[Chris Dickerson]

I managed to get a simple example working. The notes in the MessageBus class file indicates that if I use a more unique class as the type I can further make the message unique (as well as pass more than just a string).

Window1:

        private void method(object obj)

        {

            MessageBox.Show(this, "Window1" + obj.ToString());

        }

        private void Window_Loaded(object sender, RoutedEventArgs e)

        {

            MessageBus.Current.Listen<object>("Window1").Subscribe(x => method(x));

        }

Window 2:

MessageBus.Current.SendMessage<object>("bleah", "Window1");

Now I can figure out how to get this to work with IReactiveCommand (if that's valid, binding to a button as well as wired for the MessageBus).

[Chris Dickerson]

Thanks Paul, those examples make sense, appreciate the shorthand too. 

Just an aside.. ReactiveCommand.Select, it says it "Projects each element of an observable sequence into a new form",  would a ReactiveCommand ever be more than just a single item in a sequence? Or is using Select in your example, just a convenience? 

[Paul Betts]

A ReactiveCommand is an infinite sequence, every time you invoke the command
it's an element in that sequence. Just like the sequence of MouseMoves doesn't
end.

--
Paul Betts <pa...@paulbetts.org>

> > Paul Betts <pa...@paulbetts.org <javascript:>>
> >