Subscribing to real-time data

For this exercise we will be subscribing to a real-time feed from Twitter that is being pushed through the Kwwika service. This feed can be subscribed to on the/KWWIKA/TWITTER/HASHTAGS/TECH topic and contains all real-time Tweets containing the hashtag #tech

Subscribe

Subscribe to the topic /KWWIKA/TWITTER/HASHTAGS/TECH using the kwwika.Connection.subscribe method. Pass in a subscription listener to receive updates on the subscribed topic.

Handle updates

From the topicUpdated callback build a string that represents some HTML you would like to add ot the web page.

There are a number of fields available on the mUpdate parameter (map object):

• Text
• ScreenName
• InReplyToScreenName
• InReplyToStatusId
• InReplyToUserId
• UserName
• Id
• Source
• Truncated
• Favourited
• UserFollowersCount
• UserProfileImageUrl

Heres an example mUpdate object for /KWWIKA/TWITTER/HASHTAGS/TECH in object literal notation:

({InReplyToScreenName:"techcores", CreatedAt:"5/15/2010 6:17:11 PM", Truncated:"false", Text:"#tech Auto-dimming electrochromic panels reduce glare when driving (video) http://ow.ly/17nTwo", ScreenName:"justindnewton", UserFollowersCount:"3318", Favourited:"false", TotalTweets:"112", RetweetTotal:"16", UserName:"Justin Newton", UserProfileImageUrl:"http://a1.twimg.com/profile_images/900568752/justinnewtonimg_normal.jpg", InReplyToUserId:"88088839", Id:"14048836922", InReplyToStatusId:"=", Source:"<a href=\"http://www.hootsuite.com\" rel=\"nofollow\">HootSuite</a>"})

Fields can be accessed in two ways :

var sText = mUpdate["Text"] ;

var sText2 = mUpdate.Text;

Update the web page

So, for this exercise, if you've created a div with an id "latest_div" you could do the following:

document.getElementById("latest_div").innerHTML = mUpdate.Text;

Hints & Tips

Subscribing

// Define a subscription listener object.

     var oSubscriptionListener = function() {

      this.topicUpdated = function(oSub, mUpdate) {

            // handle update

      };

      this.topicError = function(oSubscription, sReason) {

            // handle errors

      }

}

var oSub = oConn.subscribe("/KWWIKA/TWITTER/HASHTAGS/TECH", oSubscriptionListener);

oConn is the connection object you got in Exercise 1 when you connected.   You'll notice that you pass the topic you want to subscribe to and a subscription listener object into the subscribe method.

The next exercise is Exercise 3: More subscribing.