Jesse Liberty

I wanted to send a message from a ViewModel to its View so that the View could pop up a dialog box.  To do this, I used MVVM Light’s messaging bus.

At first, this seemed difficult because I was over thinking it.  It turns out to be painfully easy.

In the ViewModel I created a NotificaitonMessage.  You can pass any kind of object through the Message Bus, but to keep things simple, I used a string as my token.  All I had to do was instantiate a NotificationMessage object and then call a static method on the supplied  Messenger class:

var myMessage = new NotificationMessage("change");
 Messenger.Default.Send(myMessage);

This sends off my message like a message in a bottle.  The sender (my ViewModel) has no idea if the message will be received by any other class (ViewModel or View).

In the View I registered to receive this notification.  To do so, I put one line in my constructor,

 Messenger.Default.Register<NotificationMessage> (this, NotifyMe);

NotifyMe is a delegate, pointing to a method named NotifyMe.  You could, of course, just use a lambda expression.

NotifyMe receives a parameter of type NotificationMessage.  That message has a property Notification which contains the object you sent (e.g., “change”).

       public void NotifyMe (NotificationMessage message)
       {
          string token = message.Notification;  // "change"
          DisplayAlert ("Test", "Hi!", "OK");
       }

In the code shown, I extract the string “change” but I don’t do anything with it.  I just extracted it to show how it is done.

That’s it.  I’ve successfully told the View to display an alert by firing off a message in the ViewModel.  Handy, quick, easy.

I was pleased and proud to be interviewed on Away From The Keyboard, talking about my history in the industry.  Makes a good bookend with my talk with Shawn Wildermuth on Hello World.

Great fun.

[Updated 11:26 EDT]

macOS Sierra is here (goodbye Mac OSX)

It has only a few new features, most notable of which is Siri on the Mac.

Siri works ok, not great.  And even when she is fully  understanding my requests, there is only so much she can do.  Great for looking up faces in your photos, good for looking up things on the web, not so great for making phone calls, and why would I want her to open Word when I can do so myself in 1/2 the time?

A perhaps more important feature is the ability to copy and paste from the Mac to the phone.  That is very cool — not needed often, but nice when you do need it.

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