Tuesday, December 27, 2011

Refreshing the column in rails

It may be possible that your database is shared with multiple applications and you data are frequently changing. You can manually refresh the object by:

stock = Stock.find_all
loop do
puts “price = #{price}”
sleep 60

Monday, December 19, 2011

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.

Thursday, November 24, 2011

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:

    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.

Monday, October 10, 2011

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 :



Thursday, September 22, 2011

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'

Thursday, September 1, 2011

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


    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

 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 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" />
      <input type="submit" value="Update"/>


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 data-role="content">
    <ul data-role="listview">
         <% @youtubes.each do |youtube| %>
            <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>
    <% end %>      


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 

Tuesday, August 16, 2011

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 :
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 client v2.1.1 connected to redis://localhost:6379/0 (Redis v2.2.2)

Some Redis Examples
> $redis.set("website","itsallaboutruby")
=> "OK"

Monday, August 1, 2011

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
  • Linda Morris
  • Geetanjali Sawant
  • Melwyn D'Sa
Production Coordinator
  • Melwyn D'sa
  • Cover Work
  • Melwyn D'sa

This is the link to buy the book :Rhomobile Book

Sunday, July 3, 2011

$(‘#form_id’).submit() does not work with Rhomobile+ jQtouch

If you are using Rhomobile and jQtouch together you may find that  $(‘#form_id’).submit();  will not work.  Use jQT.submitForm(‘.current form.yourFormClass’); instead of submit.

Thursday, May 5, 2011

Rhomobile IDE

 You may be wondering which IDE should I use for Rhomobile Development?

I’m writing this mainly as a guide for people just getting started with Rhomobile, so don’t freak out if you don’t see any editor. These are just some that I recommend you try if you’re first starting. 
All of these are free. 

You can use any IDE of your choice which support ruby.
One of the Best IDE for ruby are:
  • TextMate
  • NetBeans
  • Eclipse
  • Rhohub Online Editor
  • RhoStudio

I love to use Textmate on my Mac. For Windows you can use RhoStudio.

RhoStudio Beta,the IDE for Rhomobile technology is launched recently. It is a local Eclipse IDE that performs app generation, editing, and build of all Rhodes projects. 

So Start coding..enjoy...

Thursday, April 14, 2011

Review:Rhomobile vs Appcelerator/titanium vs PhoneGap Which one is Best?

What all Products are available for Mobile Application Development?
To know about Native application,Web application and Hybrid application follow this link

There are plenty of players available for Mobile Development.
The major frameworks in market are
·       Appcelerator Titanium
·       DroidDraw
·       PhoneGap
·       Rhomobile
·       Application Markup Language (AML) etc.

Each of these frameworks has its own advantage and disadvantage. The choice of frameworks depends on project’s requirements.
Each platform for mobile applications also has a development environment which provides tools to allow a developer to code, test and deploy applications into the target platform environment. There are also Legacy Providers which are platform specific. 

In following table we have shown comparison of Rhodes with Legacy Provider and other frameworks.

Legacy Providers
Other Framework
Support all Smart Phone
Native UI
App Language
Model View Controller
Barcode/Signature Capture
Support all OS
Native Push API
Hosting Facility

  (Source : www.rhomobile.com )

Why Rhomobile is different from other products in market?

·       Model View Controller
Most of the other framework available in market are based on HTML and JavaScript . Hence other frameworks force us to put all business logic into the view and JavaScript. However, as Rhodes is ruby based framework and its structure is similar to popular framework Rails it also support Model View Controller, so code written with Rhodes is more structured and easy to understand.

·       Cross Platform Support for All Devices
Rhodes supports far more device operating systems than any other framework: iPhone, Android, Windows Mobile, BlackBerry and Symbian. The best thing is you have single code base from which you can build application for different smart phone. It does not work legacy way that we have to write seperate code for different types of phones.

·       Offline Capabilities using Rhosync
Rhomobile supports local synchronization of data. Older sync servers don’t support modern smartphones such as iPhone and Android. Most iPhone developers that need sync just end up writing their own synchronization code or process. As we can synchronize the data using Rhosync it provide offline Capabilities. We can work even if you are offline.

·       Object Relational Manager
Rhodes provides inbuilt Object Relational Manager called Rhom. It is similar to Active Record in Rails but with basic functionality only. It helps us to write queries without thinking about which database is being used by phone

·       Rapid Development
One of the interesting features of Rhodes is that it imposes some fairly serious constraints on how you structure your applications which help us for Rapid development. Rhomobile products are properly structured and well organized which enforce  us to do rapid development. Modern web developers have found Rhodes to be very comfortable, familiar and massively productive.

·       Scalable Sync Server
The Sync Server uses NoSql Database which makes it scalable. In addition, RhoSync has several compelling advantages over other sync servers yet built. Specifically it is the only sync server that has a built-in “no SQL”  Redis key value store, making it more scalable than other sync servers who offers internal relational database servers for caching. RhoSync also performs its push-based sync using the native smart phone push SDKs, which no other sync server does.

·       Liberal use of code generation
 Rhodes/RhoSync can write lot of code for you. For example, when you need a class to represent a table in your database, you don't have to write most of the methods. Rhodes even offers an application generator that creates an initial app based on the structure of your models or business objects in your app. It’s very similar to the scaffolding offered by most modern web frameworks with basic “list/create/read/update/delete objects” functionality. For each basic CRUD action, views in HTML are also offered. App developers spend most of their time just modifying views as they see it. No other framework provides an app generator, nor does any SDK. Rhodes looks at the table's definition and creates most of the class. You'll find that you're writing only a fraction of code compare to other frameworks.

·       Metadata
Every enterprise application that is used to run a company’s core business has a different schema for its business objects. For example, every application has varying and customized structure that changes with time. It is not possible to install the client application again and again for a small change. Metadata framework provides a way to handle the view from Rhosync server. It also provides validation and custom template.

·       Hosted Development and Build
Rhomobile also provides a hosted management and Build through Rhohub. We can deploy Rhosync app and build our Rhodes code for different phones with it. No other products in market offer such functionality or feature as of now.
PhoneGap is an HTML5 app platform that allows you to write native applications with web technologies and get access to Native Capabities of phone with ease. PhoneGap uses standards-based web technologies to bridge web applications and mobile devices.

Strengths :

  • Can use HTML5 and CSS3
  • Deploy your app to Multiple Platforms (Symbian and Bada is also supported)
  • Access Native Features
  • Use JavaScript to write your code
  • Licence under Apache Software Foundation
  • Very well documented
  • PhongGap APIs are more generic and can be used on different platforms such as iPhone, Android, Blackberry, Symbian, etc 
  • No MVC
  • No ORM

Appcelerator Titanium
Appcelerator Titanium is an open source mobile application development tool for iPhone and Android. We can also create Desktop application with titanium. It allows you to code apps with HTML, CSS and JavaScript. Titanium primarily uses Javascript and JSON code to write your Native application. It supports Ruby, Python, and PHP scripts for broad developer coverage. If you are creating any social media mobile app then it is better option as Facebook, Yahoo etc API is available with titanium.
Documentation is available here: http://developer.appcelerator.com/documentation


  • Compiles to truly native application code, not HTML5
  • Very large library of APIs for all kinds of activities and data access
  • Uses Javascript/JSON for primary language
Titanium appears to be more feature rich than PhoneGap by bridging more mobile phone functions to javascript. 

  • Only support iphone and Android
  • No MVC and ORM
Rhodes and Phonegap does NOT compile your html, css or javascript code into "native bits". When the application runs, these resources use  UIWebView control and run there. From architectural standpoint, these the frameworks are very similar. 

Also i have presentation in RubyConfIndia 2012 about "Which Mobile platform should i choose?"

Sunday, March 27, 2011

Changing Rhosync URL dynamically

We may need that we want to change rhosync server URL dynamically. We can change using  Rho::RhoConfig API


Calling the function above will do the following:

  • Update the in-memory syncserver for the SyncEngine 
  • Perform a logout to make sure the session for the old syncserver is removed
  • Write the new syncserver property to rhoconfig.txt

Tuesday, February 22, 2011

Rhomobile javac invalid flag error

Sometime we try to run rake run:bb and we get following error:

[...stuff deleted]

cp -r platform/bb/build/../hsqldb/src/com/rho/file/
PersistRAFileImpl.java C:/Doc
uments and Settings/mrcorba/storemanager/bin/tmp/vsrc/com/rho/file
        executing javac
PWD: C:/Ruby19/lib/ruby/gems/1.9.1/gems/rhodes-1.5.4
CMD: "C:/Program Files/Java/jdk1.6.0_03/bin/javac.exe" -g -d "C:/
Documents and S
ettings/mrcorba/storemanager/bin/tmp" -classpath "C:/Documents and
rba/storemanager/bin/RhoBundle.jar;C:/Documents and Settings/mrcorba/
r/preverified/RubyVM.jar" -bootclasspath "C:/Program Files/Research In
ackBerry JDE 4.6.0/lib/net_rim_api.jar" -source 1.3 -target 1.3 -
nowarn "@C:/Doc
uments and Settings/mrcorba/storemanager/bin/tmp/vsrc_build.files"
build/hsqldb_build.files @platform/bb/build/rhodes_build.files
javac: invalid flag: C:/Documents
Usage: javac
use -help for a list of possible options

Error compiling java code 

Try to move your app into a folder without spaces.
 Ex If you project is in C:\some directory\Rhodes_application then put your applicaton in  C:\some_directory\Rhodes_application
This is because sometime Rhodes is not able to count white spaces.

Friday, January 28, 2011

Rhomobile talk in Pune Rails Meetup

Today Akshat and I got a chance to speak about Rhomobile in Pune Rails meetup. It is good to see that lot of people are showing interest in Rhomobile. 
You can download PPT and code which we showcase from following link :
Code on github :

Monday, January 24, 2011

Improving performance of your Rhodes application #Rhomobile

I am listing out the way to improve the performance of Rhodes application:
  • Set MinSeverity=3 in rhoconfig.txt for production. Otherwise it will log all your activities and will affect your performance.
  • Set bb_loadimages_async=1 in rhoconfig.txt. In this mode next page opens, while the images are being loaded in the background 
  • Minimize the possible external files like CSS and Javascript. If possible include these file in layout.erb. 
  • Use Fixed schema instead of Property Bag if you schema is fixed and not expected to change. You can refer this link to understand it better http://itsallaboutruby.blogspot.com/2011/01/difference-between-propery-bag-and.html
  • Avoid using XML as they are slow, instead try use JSON.
  • Try using Rho JSON for parsing, if you have been using JSON. Rho JSON will minimize your sync time.
        parsed = Rho::JSON.parse("[{\"count\":10}]")

     You can refer following link to dig it in detail:

Courtesy: @adamblum and akoc :

  • Bulk Sync :  Bulk sync will make huge deference in performance while syncing from rhosync.

  •   Push : Rhosync Push API also give a edge on performance while syncing.

P.S : If anyone can suggest any other ways he is welcome to comment on the Blog :) 


Thursday, January 20, 2011

Difference between Propery Bag and Fixed Schema #Rhomobile

Rhomobile provide a mini ORM called Rhom. It is similer to Active Record of Rails but with less features.It provides a high level way to make the local database easier to program. That database is SQLite on all platforms except BlackBerry where it is HSQL.  

We can choose to store data in two way Propery Bag or Fixed Schema

Property Bag
All the data is store in stores in single table. Property bag is a db table which contains object id/attribute/value triplets and therefore set of attributes for each object is arbitrary.

  • It is simple to use, no require for specifiyng attributes before use
  • we don't need to migrate data if  we add/remove attributes
  • Size is 3 times bigger than fixed schema
  • Slow while sync

 This is how model look for PropertyBag:

class Employee
  include Rhom::PropertyBag

  # Uncomment the following line to enable sync with Employee.
  # enable :sync

  #add model specifc code here

Fixed Scema
Fixed schema is a regular db table with fixed set of columns (attributes)

  •   Smaller size, you can specify index for only required attributes
  •   Faster sync time then Property bag
  • You have to support all schema changes
 This is how fixed schema model looks :

class Employee
  include Rhom::FixedSchema

  # Uncomment the following line to enable sync with Employee.
  # enable :sync
  set :schema_version, '1.1'
  property :name, :string
  property :age, :string
  property :company, :string
  property :address, :string
  property :gender, :string
  property :salary, :string
  #add model specifc code here

Note : You have to reset database if you change the property

When you use Fixed Schema model application developer is responsible for sql schema. So when you add or delete some properties or just change app logic you may need to perform data migration or database reset.
So if you have to add a column in a table we have to add a property and then reset the Device.

To create a index in fixed schema we will write following line in model :
index :by_name_tag, [:name, :tag] #will create index for name and tag columns  

To create a primary key in fixed schema we will write following line in model :
unique_index :by_phone, [:phone]

Choosing in between PropertyBag and FixedSchema depend on you requirement.