Rails Observers vs Callbacks

Rails Callback

Callbacks are methods that get called at certain moments of an object’s life cycle. That means that it can be called when an object is created, saved, updated, deleted, validated, or loaded from the database.

A callback is more short lived. And you pass it into a function to be called once. 

Rails Observers

Observer is similer to Callback but it is used when method is not directly related to object lifecycle. The other difference is an observer lives longer and it can be attached/detached at any time. There can be many observers for the same thing and they can have different lifetimes. 

The best example of Observer is that it could be “send registration confirmation emails” As we can argued that a User model should not include code to send registration confirmation emails so we will create observer for this.

Rhodes Iphone Build using Xcode

In this post we will create Rhodes build from Xcode. Though we can do this by rake run:iphone for development and rake run:iphone:production for Production but for better understanding and advance configuration we can do the same with Xcode. 

To start quickly,  these are the prerequisite:

•        Valid Provision Profile should be installed.
•        Valid Certification should be installed.

For getting these Certification login to Apple Development Center and navigate to iOS Provisioning Portal.

Now to get started follow these steps:

•    Go to your project folder from Terminal and type:          

             $rake switch_app

The switch_app command changes the rhobuild.yml in the Rhodes source code folder to point to your application, as in the following example for a Rhodes application named Store in the user’s home folder:

env:   

    app: /Users/Name_Of_User/Application_name

  

• Now run the following command to tell Rhodes to set up the Xcode environment for your Rhodes application:

          $ rake build:iphone:setup_xcode_project

•    Open rrhorunner.xcodeproj project. This will open your application in Xcode. You can find this project in Gems folder of ruby -> Rhodes-> Platform-> iphone. After opening the project we can see rhorunner project is open in Xcode.

• To run the application select rhorunner project and then select where you want to run the application. If you have connect iOS device it will appear on list for example in given image I have connected my iphone "Abhishek Nalwaya's iPhone"

If we select "Abhishek Nalwaya's iPhone" and click on Run then it will automatically create the build and install the application on the device. To run in the simulator you can select from the list. 

Debugging Notes: 

• Make sure you have register the device to appstore for testing.
• Make sure you have selected correct Code Signing 

• If you want to restore the XCode use following command:

              $rake build:iphone:restore_xcode_project

If you face any issue feel free to comment on this post.

Motorola Solutions acquires Rhomobile

It is officially announced yesterday that Motorola Solutions has acquires Rhomobile. So this ruby based Mobile Framework is now part of  Motorola Solution. Few week back it was announced that HTML5 based Mobile Framework Phonegap is acquire by Adobe.  So is it Mobile/HTML5 buzz?

Motorola  announced the availability of Motorola RhoElements, a state-of-the-art web-based application framework. It is designed to allow businesses to quickly and cost-effectively develop and deploy web-based applications on existing Motorola Windows Embedded Handheld (formerly known as Windows Mobile) and Windows Embedded Compact (Win-CE) mobile computers as well as Motorola’s recently announced ET1 Android-based enterprise tablet.

These are the key notes of acquisition:

• All Rhomobile products will continue to be sold and supported globally.  
• Rhodes will continue to be available open source under the MIT License.
• They are committed to supporting the Rhomobile community and continuing the open source heritage of Rhodes
• They also announced their updated Windows Mobile focused mobile browser  now called RhoElements. 
• Motorola Solutions will provide the scale, resources, industry knowledge, and broader base of partners and channels to accelerate universal adoption of Rho technology

Reference :
http://mediacenter.motorolasolutions.com/Press-Releases/Motorola-Solutions-Offers-Industry-s-First-Framework-for-Developing-HTML5-Applications-on-Windows-Embedded-Handheld-and-Windows-CE-Devices-3741.aspx

http://www.marketwatch.com/story/motorola-solutions-offers-industrys-first-framework-for-developing-html5-applications-on-windows-embedded-handheldtm-and-windows-cetm-devices-2011-10-10

http://techcrunch.com/2011/10/10/motorola-launches-rhoelements-an-html5-framework-for-building-mobile-apps-for-enterprise/

git branching

There is very nice example given by Satish Talim on git Branch on Google +. Though it is basic but I like the example, that's why sharing the link:

Satish Talim - Google+ - The Free, Online Git / GitHub 101 Course ( Link to Day 7 -…:

'via Blog this'

Rhomobile Ipad Example- You Tube Client

We will create a Rhomobile ipad application which will search youtube videos and will playback this videos. It is just an example and our purpose is to explore Rhomobile AsyncHttp methods. We will connect to You tube search API. 

Step 1.) Create Rhodes application :

              rhogen app youtube_client

   

Step 2.)  Go to application directery:

              cd youtube_client/

Step 3.)  Create a controller Youtube

Step 4.) Create action search and search_result in youtube_controller.rb

   def search

   end

    def search_result

        you_tube_url = "http://gdata.youtube.com/feeds/api/videos?q=" + @params['name'] + "&max-results=5&v=2&alt=jsonc"

        @youtubes= Rho::AsyncHttp.get(

                                       :url => you_tube_url

                                       )["body"]["data"]["items"]

    end

 We are using AsyncHttp to call You Tube search API. And @params['name'] contain the search term.

5.) Create search.erb 


<div data-role="page">


  <div data-role="header" data-position="inline">
    <h1>Search You tube</h1>
    
  </div>


  <div data-role="content">
    <form method="POST" action="<%= url_for :action => :search_result %>">    
          <div data-role="fieldcontain">
            <label for="name" class="fieldLabel">Name</label>
            <input type="text" id="youtube[name]" name="name" />
          </div>
      
      <input type="submit" value="Update"/>
    </form>
  </div>


</div>

6.) Create search_result.erb and add following code:


<div data-role="page" data-add-back-btn="false">


  <div data-role="header" data-position="inline">
    <h1>Search result</h1>
  </div>


  <div data-role="content">
    <ul data-role="listview">
      
         <% @youtubes.each do |youtube| %>
        <li>
      <center>
            <span class="title">
<%= youtube["title"] %></span><br>
<iframe width="400" height="400" src="http://www.youtube.com/embed/<%= youtube["id"]%>" frameborder="0" allowfullscreen></iframe></center>
<span class="disclosure_indicator"></span>
      
        </li>
    
    <% end %>      
    </ul>
  </div>


</div>



7.) Link the search.erb to home page(by default it is index.erb in app folder.

8.) If you creating it for ipad add following line in build.yml under iphone.

      emulatortarget: ipad

If you creating this app for iphone or Android you can skip this step.

You can Download this code from : https://github.com/nalwayaabhishek/YouTubeClient 

Connect Rails and Redis

These days Redis is getting very popular because of its document style storage and high performance. It is a persistent in-memory key-value store written in C by Salvatore Sanfilippo. Redis is an open source, advanced key-value store. It is often referred to as a data structure server since keys can contain strings, hashes, lists, sets and sorted sets.

When to use Redis :

• You want to access the data very fast.
• Your data set is not big and it can fit in available RAM
• And your data is not very critical if it loose due to any failure 

Install redis:
Download and install from http://redis.io/download


Start Redis
Go to terminal and type :
./redis-server
By default it will run on port 6379

Connecting Redis with Rails 
Once Redis is installed and running follow these steps:
1.) Open gemfile
gem 'redis', '2.1.1'
2.) Then go to your application directory from terminal and execute:
bundle install
3.)Go to following directory /config/initializers/ and create a file redis.rb
4.) Write the following code in redis.rb
$redis = Redis.new(:host => 'localhost', :port => 6379)
By default redis run on 6379, if you are running on different port change this port attribute.

All configuration is completed and now you can use $redis global variable from your rails application.
Checking the connection :
Go to rails console and type following command
 >$redis
=> Redis client v2.1.1 connected to redis://localhost:6379/0 (Redis v2.2.2)

Some Redis Examples
> $redis.set("website","itsallaboutruby")
=>"OK"
>$redis.get("website")
=>"itsallaboutruby"
>$redis.set("count",1)
=> "OK"
>$redis.incr("count")
=>2

Rhomobile Book

Finally My Book on Rhomobile has been publish with pactpub.

Now Its time to say Thanks.

I would like to express my gratitude to my family and friends especially Akshat Paul, Manu Singhal, and Anuj Bhargava who saw me through this book, who provided support, talked things over, read, wrote, offered comments, without which conceiving this book wouldn't have been possible.

Also, I would like to thank Sarah, Neha, Kartikey, Shubhanjan, and the PacktPub team who allowed me to quote their remarks and assisted in the editing, proofreading, and design. Writing a book was not my cup of tea but they made this complicated journey effortless.

Also I want to say big thanks to Reviewers:

Brian Moore :

Brian Moore is a Senior Engineer at Rhomobile, father of two, and quintessential hacker.

Brian began coding at the age of 12. His early love for everything technological led to a job with Apple shortly after high school. Since that time Brian has worked at a series of start-ups and tech companies taking on interesting technical challenges. Brian has become the

technical face of Rhomobile as he leads the Rhodes community in the latest Rhomobile innovation during the Friday webinars. When not guiding the next generation of Rhodes developers or hacking on a new debugger, Brian can be found climbing a hill in a remote Southern California desert in his baja bug.

Deepak Vora is a consultant and a principal member of the NuBean.com Software Company. Deepak is a Sun Certified Java Programmer and Web Component Developer, and has worked in the fields of XML and Java programming and J2EE for over five years. Deepak is the co-author of the Apress book Pro XML Development with Java Technology and was the technical reviewer for the O'Reilly book WebLogic: The Definitive Guide. Deepak was also the technical reviewer for the Course Technology PTR book Ruby Programming for the Absolute Beginner, and the technical editor for the Manning Publications book Prototype and Scriptaculous in Action. Deepak is also the author of the Packt Publishing book JDBC 4.0 and Oracle JDeveloper for J2EE Development, Processing XML documents with Oracle JDeveloper 11g, and EJB 3.0 Database Persistence with Oracle Fusion Middleware 11g.

Other contributors:


Acquisition Editor

• Sarah Cullington

Development Editor

• Neha Mallik

Technical Editors

• Ajay Shanker
• Mohd. Sahil

Project Coordinator

• Shubhanjan Chatterjee

Proofreader

• Linda Morris

Indexer

• Geetanjali Sawant

Graphics

• Melwyn D'Sa

Production Coordinator

• Melwyn D'sa
• Cover Work
• Melwyn D'sa

This is the link to buy the book :Rhomobile Book