Barry.js - Keep your models up-to-date
Barry, the old gossip, is a simple JavaScript/Node.js library that keeps your client-side models synchronized with your server-side state.
Barry really loves Angular.js <= Socket.IO => Node.js, but all the actual integration with those tools consists of just a few lines of JavaScript, so you can easily write the glue to hook it into pretty much anything you want.
On the server-side you first define an endpoint. This is where you specify how clients will connect and how they'll be able to talk to Barry. Here is how you set up a Socket.IO endpoint:
var barry = ;
Your endpoint will provide a number of services. Let's say we want a service where we can get the current number of connected clients. Barry provides a number of pre-made types of services, one of which is a ScalarService, which is a service where people simply subscribe to a single value, like a string or, in our case, a number.
var barry = ;var clientCount = barry;clientCountvalue = 0;barry;
That's it! Our server is ready to use. Let's see how an Angular.js-based client would use our brand-new service:
{$barry;}
And now we can add a binding to our template:
We currently have ??? connected clients.
Pretty easy, right? Now Angular and Barry are going to completely take care of keeping this value updated for us. Even better: Barry takes care of loading the initial value when the controller is instantiated and unsubscribing when the user navigates away from the page.
But let's look at a more interesting example. This time we have a dictionary of values, a key/value store basically, and we want clients to be able to subscribe to some prefix of keys.
var barry = ;var phonebook = barry;phonebook;
// Kevin Mitnick is a badass hacker, so his phone number magically changes // every two seconds! Ok, maybe not, but it's still good for our demo. setInterval(function () { var value = phonebook.dict["Mitnick, Kevin"]; value = value.slice(0, 8) + ((+value.slice(8) + 3943) % 9000 + 1000); phonebook.dict["Mitnick, Kevin"] = value; }, 2000);
As for the client, let's code the UI first this time:
``` html
<div ng-controller="PhonebookCtrl">
<p>Start typing a last name and matching entries will be automatically displayed:</p>
<p><input type="text" ng-model="prefix"></p>
<ul id="suggestions" ng-show="suggestions.$b.loaded">
<li ng-repeat="name, no in suggestions">
<strong>{{name}}:</strong> {{no}}
</li>
</ul>
<p ng-hide="suggestions.$b.loaded">Loading suggestions...</p>
</div>
So we want to show a list of suggestions like an autocomplete of what the user entered. The interesting part is that this autocomplete will be self-updating!
You'll notice also that we're using a special value called $b. This contains a bunch of meta-information like what the state of the model is - is it initialized, is it live-updating, etc. In this case we're using $b.loaded
to find out if it is initialized.
{var consumer = $barry;$scope;}
Another new trick: You can switch out services on the fly. So we start with a null service (which will tell Barry to just set the model to null) and once the user enters a prefix it will move to the correct service, subscribing and unsubscribing as required.
barry.service('clients', { init: function (req, model) {
}, apply: function (change);
$b
)
Meta-information ($b.loaded
(Boolean)
True, if the model contains data, false if it doesn't.
$b.updated
(Integer)
Timestamp of the last update to the model (client time).
$b.updatedServer
(Integer)
Timestamp of the last update to the model (server time).