Add singleton subscriptions

README.md

@@ -223,6 +223,22 @@ Now, when we publish to a channel, we can pass the `:except` option, with the cu
 
 Now, the original client won't get the duplicated chat message, even if it's subscribed to the __/chat__ channel.
 
+##Singleton subscription
+
+Sometime you need to have only one subscription to a channel, regardless the number of times you call `subscribe`. It may be useful when you subscribe in an AJAX callback. To do so, you can use `singleSubscribe`.
+
+jQuery('.user a.follow').live('click', function(event){
+  jQuery.post(this.href, function(data, status, xhr){
+    var channel = "users/" + data.user.id + "/feed";
+    juggernaut.singleSubscribe(channel, function(feedEntry){
+      console.log("Got new feed entry: " + feedEntry);
+    }
+  });
+});
+
+Even if the user click many times to follow an user, each new messages of this users's feed will be pushed to the client only once.
+
+
 ##Server Events
 
 When a client connects & disconnects, Juggernaut triggers a callback. You can listen to these callbacks from the Ruby client,

client/vendor/assets/javascripts/juggernaut.js

@@ -6,8 +6,9 @@ var Juggernaut = function(options){
   this.options.host = this.options.host || window.location.hostname;
   this.options.port = this.options.port || 8080;
 
-  this.handlers = {};
-  this.meta     = this.options.meta;
+  this.subscriptions = {};
+  this.handlers      = {};
+  this.meta          = this.options.meta;
 
   this.io = io.connect(this.options.host, this.options);
 
@@ -67,9 +68,20 @@ Juggernaut.fn.subscribe = function(channel, callback){
   }
 };
 
+Juggernaut.fn.singleSubscribe = function(channel, callback){
+  if ( this.subscriptions[channel] ) return false;
+  else {
+    this.subscribe(channel, callback);
+    return(this.subscriptions[channel] = true);
+  }
+};
+
 Juggernaut.fn.unsubscribe = function(channel) {
   if ( !channel ) throw "Must provide a channel";
 
+  if ( this.subscriptions[channel] ) 
+    this.subscriptions[channel] = false;
+
   this.unbind(channel + ":data");
 
   var message     = new Juggernaut.Message;