Added JavascriptHelper#periodically_call_remote in order to create areas of a page that update automatically at a set interval #945 [Jon Tirsen]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1108 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

2 files changed, 38 insertions, 0 deletions

diff --git a/actionpack/lib/action_view/helpers/javascript_helper.rb b/actionpack/lib/action_view/helpers/javascript_helper.rb
index 59765f9737..ba418b15b3 100644
--- a/actionpack/lib/action_view/helpers/javascript_helper.rb
+++ b/actionpack/lib/action_view/helpers/javascript_helper.rb
@@ -71,6 +71,15 @@ module ActionView
         link_to_function(name, remote_function(options), html_options)
       end
 
+      # Periodically calls the specified url (<tt>options[:url]</tt>) every <tt>options[:frequency]</tt> seconds (default is 10).
+      # Usually used to update a specified div (<tt>options[:update]</tt>) with the results of the remote call.
+      # The options for specifying the target with :url and defining callbacks is the same as link_to_remote.
+      def periodically_call_remote(options = {})
+         frequency = options[:frequency] || 10 # every ten seconds by default
+         code = "new PeriodicalExecuter(function() {#{remote_function(options)}}, #{frequency})"
+         content_tag("script", code, options[:html_options] || {})
+      end
+      
       # Returns a form tag that will submit using XMLHttpRequest in the background instead of the regular 
       # reloading POST arrangement. Even though it's using Javascript to serialize the form elements, the form submission 
       # will work just like a regular submission as viewed by the receiving side (all elements available in @params).
diff --git a/actionpack/lib/action_view/helpers/javascripts/prototype.js b/actionpack/lib/action_view/helpers/javascripts/prototype.js
index 5dc41e36dd..1ab50882c4 100644
--- a/actionpack/lib/action_view/helpers/javascripts/prototype.js
+++ b/actionpack/lib/action_view/helpers/javascripts/prototype.js
@@ -613,3 +613,32 @@ Effect.Appear.prototype = {
   }
 }
 
+/*--------------------------------------------------------------------------*/
+
+PeriodicalExecuter = Class.create();
+PeriodicalExecuter.prototype = {
+  initialize: function(what, frequency) {
+    this.what = what;
+    this.frequency = frequency;
+    this.currentlyExecuting = false;
+    
+    this.registerCallback();
+  },
+  
+  registerCallback: function() {
+    setTimeout(this.onTimerEvent.bind(this), this.frequency * 1000);
+  },
+  
+  onTimerEvent: function() {
+    if (!this.currentlyExecuting) {
+      try { 
+        this.currentlyExecuting = true;
+        this.what(); 
+      } finally { 
+        this.currentlyExecuting = false;
+      }
+    }
+    
+    this.registerCallback();
+  }
+}