Poetry of Programming

Its about Ruby on Rails – Kiran Soumya


Driver Error: Svn Merge

The ‘svn merge’ command compares two trees, generates a patch, then
applies that patch to a working copy. Yes, you have complete freedom
to compare any two trees, and thereby generate any patch you want. But
that does *not* mean that ‘svn merge’ always will do what you want.
It’s *your* responsbility to make sure that the patch being produced
makes sense, and cleanly applies to your working copy.      
Skipped ‘src’
Skipped ‘src’
Skipped ‘src\au’
Skipped ‘src\au\com’
Skipped ‘src\au\com\forward’
Skipped ‘src\au\com\forward\codeSections’
A src\au\com\forward\codeSections\DesignNotes.txt
A src\au\com\forward\codeSections\CodeSections.java
Skipped ‘src\au\com\forward\codeSections\testFiles’
A src\au\com\forward\codeSections\testFiles\testin.cs
Skipped ‘docs’
Skipped ‘docs’
A docs\htmldoc.exe 

See those skipped messages? That indicates driver error. The merge
command is trying to add and remove certain directories because they’re
not related to each other at all. Please read this section of chapter
4, regarding ancestry:


Then after reverting, try the merge again with the –ignore-ancestry

So, It is like this what I have implemented,

> Taken a latest production copy as my_working_copy

> Merged the dev branch with production branch under  my_working_copy

svn merge –ignore-ancestry prod_branch_url dev_branch_url my_working_copy/

> And this is how we avoid the driver error.

> Check for conflicts under my_working_copy

Fix the conflicts always in favour of Clients Requirements.

Else if no conflicts, check in the merge to production

Finally, Say The END to the project !!!

Next is What ?  [ Samsung Adv :) ]


Avoid SVN updates for External Rails Plugins in your Application

Make sure you are in the root of your app and do:
svn propedit svn:externals vendor/plugins
Just delete the line(s) of the plugins you no longer want.

If you get the following error then you need to set your environment variable.
svn: None of the environment variables SVN_EDITOR, VISUAL or EDITOR is set, and no ‘editor-cmd’ run-time configuration option was found

For example, you can set the SVN_EDITOR to use Vi editor from your unix prompt like

export SVN_EDITOR='”/bin/vi”‘

In Windows, instead of export, it is

set SVN_EDITOR=c:/windows/notepad.exe (for notepad)


set SVN_EDITOR=”C:\Program Files\Posix Tools\bin\vi” (for Vi editor)


I need an individual file to be migrated in Rails

Rails migrations are great, they allow continual evolution of database schema. Sometimes, especially when prototyping, I hate to run migrations down and up and load data, just to make small independent change in database table. In this situations I run only specific migration:

ruby script/runner 'require "db/migrate/005_create_blogs"; \n
ruby script/runner 'require "db/migrate/005_create_blogs";\n

This is much typing (for just one migration at least 😉 so here is the rake task to do the same:

namespace :db do
  task :migrate_one => :environment do
    file = Dir["db/migrate/#{ENV["VERSION"]}_*.rb"].first
    migration_class = file.scan(
    migration_class.migrate(:down) unless ENV["DIRECTION"] == 'up'
    migration_class.migrate(:up) unless ENV["DIRECTION"] == 'down'

Put this rake task in lib/tasks and you can call it with rake db:migrate_one VERSION=005. This would run migration down and up. You can also add DIRECTION=up or DIRECTION=down to control direction.

Thanks to Bojan Mihelac.


Enni Gundelu aaa?

“Enni Gundelu aaa?” Its a normal saying in telugu asking How dare you? But the exact words translation is “How many hearts you have haan?” Hmm… Well… I have two hearts !!!


Weird, Rare… and what not !

Apart from Redhat Linux, I’m also trying to set up my Rails app on a Win XP Pro machine to clarify some Ajax effects in IE. IE used system hosts file very well. But at the same time, on the same OS,  my latest Mozilla Firefox version 3.0.1 ignores the same hosts file. And this only happens when Proxy Server is used.

I didn’t understand why the configuration works only with IE, but not with
Mozilla. Makes no sense to me at all.

I am sure that I have set no proxy for localhost, and I have even tried setting no proxy for the local IP range like where my working IP lies in between. Glory ! it worked…!!!

Ofcourse, I googled with suggestions of clearing cache and subscription to 5$ monthly plan to know the solution. So this info.. is for those who uses proxy and gets weird cases like this… Enjoy the solution,  absolutely free…! :)


Ubuntu + ROR + Mysql + Svn +VPN

Every time we install Ruby/Rails/Mysql/Rmagick/Vpn on Ubuntu Gutsy or Hardy we face the same  errors again and again. Lets reduce the installation time and have a loop-back-fix-free or smooth installation experience.

After you run the CD or install Ubuntu, make sure of your Network Proxies if any, if so, you need to add the proxy url at System->preferences->Network Proxy.

then from terminal, make sure this passes…

sudo apt-get update

then for Mysql/Rails installation follow this:


and for VPN installation/connection on Ubuntu, this is the best guide:



The Hidden Treasure

 All thats nice, sweet and makes one happy is a treasure. And if anything of that sort is hidden is called the Hidden Treasure I mean… what you say?

Well, I am talking about “My fav. singer” and thats the talent of my best buddy thats hidden..


JRuby on Rails in Glassfish V3

Yesterday it happened to come across an article on “Mingle: A Rails based enterprise product” by Thoughtworks Studio.

They have used Jruby on Rails for many reasons, which made me even more curious to browse around and know on it more and more but comprises three main points…

>  Invoking Java code from Ruby

>  Or Java libraries can be used with Ruby syntax

> Deploy Rails apps on Java app servers via WAR files

(thereby the rails app can be your desktop application avoiding to create a seperate desktop app) 

The idea is seriously damn cool…


Common Query: What does Engineering doing in Software Engineering?

Writing code or set of programs result into “Software products” that are generic or customized according to the customer specifications. Now whats this Engineering doing out here? This is a quite common query…

Engineering in general terms mean “The application of Science to the design, building and use of  machines, constructions etc.”

Composing the both… the definition of Software Engineering results into

“The art,craft and science of building large and important software systems. It is an amalgam of artistry, craftsmanship and scientific thought”



Process Tool

The reason why the projects are categorized into large, medium, small, and very small is that they need to follow different processes for development.  

  Small and Very Small projects should follow only Waterfall Model, whereas Medium size projects follow either Waterfall or Iterative model. Lastly, Large projects follow either Waterfall or Iterative or Incremental model.

Therefore a large project and a very small project cannot follow the same steps while executing deliveries.    To keep a large project on track, one needs to have substantial processes in place, whereas having few processes leads to the risk of unmanaged processes, which may lead to failure.    Whereas, for a small project, having a huge process makes it a tedious and unnecessary overhead.     



Install IE6 on Ubuntu

Many of them would be knowing this before… But thanks to the reference site which am able to do the same…


IEs4Linux is the simpler way to have Microsoft Internet Explorer running on Linux (or any OS running Wine).

No clicks needed. No boring setup processes. No Wine complications. Just one easy script and you’ll get three IE versions to test your Sites. And it’s free and open source.This may be very helpful for software developers and web developers to test their applications.

IEs4Linux Installation in Ubuntu

You have to enable universe packages first. It is also recommended that you use the official winehq ubuntu package:

Open /etc/apt/sources.list file

sudo gedit /etc/apt/sources.list

Uncomment following lines in your /etc/apt/sources.list and it may be different if you are in different country instead of UK

For Ubuntu Dapper Users

deb http://uk.archive.ubuntu.com/ubuntu dapper universe
deb-src http://uk.archive.ubuntu.com/ubuntu dapper universe

For Ubuntu Edgy Eft Users

deb http://uk.archive.ubuntu.com/ubuntu edgy universe
deb-src http://uk.archive.ubuntu.com/ubuntu edgy universe

Add WineHQ APT Repository


If you want to add source packages from the repository

Currently, wine only have i386 binary packages available. If you do not use an i386 architecture, or wish to compile the package in a special or optimized way, you can build the wine package using the source repository instead. To do this, add a source repository with one of the following:

For Ubuntu Dapper Users

deb http://wine.budgetdedicated.com/apt dapper main
deb-src http://wine.budgetdedicated.com/apt dapper main

For Ubuntu Edgy Eft Users

deb http://wine.budgetdedicated.com/apt edgy main
deb-src http://wine.budgetdedicated.com/apt edgy main

Close gedit and run an update to take your new Repository

sudo apt-get update

Install wine and cabextract

sudo apt-get install wine cabextract

Now you need to download IEs4Linux script from here

wget http://www.tatanka.com.br/ies4linux/downloads/ies4linux-2.0.5.tar.gz

tar xzvf ies4linux-2.0.5.tar.gz

cd ies4linux-2.0.5

Once you are inside ies4linux-2.0.5 directory you need to run the following script to install internet explorer


This will install the internet explore in your machine.

To run IE you need to run the following command and it may be different for others this path at the end of installation it will give from where you want to run


You should see the Internet explorer opening

If try to run /root/bin/ie6 as root user you will get the following error messages so you need to run as user#/root/bin/ie6
fixme:actctx:CreateActCtxW stub!
err:imagelist:ImageList_ReplaceIcon no color!
err:imagelist:ImageList_ReplaceIcon no color!
err:imagelist:ImageList_ReplaceIcon no color!
err:imagelist:ImageList_ReplaceIcon no color!
Application tries to create a window, but no driver could be loaded.
Make sure that your X server is running and that $DISPLAY is set correctly.

If you want to check more information about this script check here


O’ Shiny Bubble !

O Shiny bubble in the eye…

do not cry !

Why feel for the ears that dont hear…

reach out your voice to the ones who’s dear !

Why feel for the things that dont happen…

reach out to them who needs you to make it happen !

Decide O shiny bubble… pain or smile…

whichever way, accept the fact O shiny bubble…

that you need to travel far mile after mile !


ROR : Important Points to be noted

> Difference between Ruby load and require:

Ruby programs may be broken up into multiple files, and the most natural way to partition a program is to place each nontrivial class or module into a separate file. These separate files can then be reassembled into a single program (and, if well-designed, can be reused by other programs) using require or load. These are global functions defined in Kernel, but are used like language keywords. The same require method is also used for loading files from the standard library.

load and require serve similar purposes, though require is much more commonly used than load. Both functions can load and execute a specified file of Ruby source code. If the file to load is specified with an absolute path, or is relative to ~ (the user’s home directory), then that specific file is loaded. Usually, however, the file is specified as a relative path, and load and require search for it relative to the directories of Ruby’s load path (details on the load path appear below).

Despite these overall similarities, there are important differences between load and require:

  • In addition to loading source code, require can also load binary extensions to Ruby. Binary extensions are, of course, implementation-dependent, but in C-based implementations, they typically take the form of shared library files with extensions like .so or .dll.

  • load expects a complete filename including an extension. require is usually passed a library name, with no extension, rather than a filename. In that case, it searches for a file that has the library name as its base name and an appropriate source or native library extension. If a directory contains both an .rb source file and a binary extension file, require will load the source file instead of the binary file.

  • load can load the same file multiple times. require tries to prevent multiple loads of the same file. (require can be fooled, however, if you use two different, but equivalent, paths to the same library file. In Ruby 1.9, require expands relative paths to absolute paths, which makes it somewhat harder to fool.) require keeps track of the files that have been loaded by appending them to the global array $" (also known as $LOADED_FEATURES). load does not do this.

  • load loads the specified file at the current $SAFE level. require loads the specified library with $SAFE set to 0, even if the code that called require has a higher value for that variable.

> To revert migrations to different version:

rake db:migrate version=19

> Task to delete all migration during deployment:

The delete command is just a convenience for executing rm via run. It just attempts to do an rm -f (note the -f! Use with caution!) on the remote server(s), for the named file. To do a recursive delete, pass :recursive => true:

Demonstrating delete [ruby]

delete #{release_path}/db/migrate“, :recursive => true




Difference between Mocks and Stubs

  • Many developers confuse the ideas behind stubbing and mocking. Stubbing simply replaces a real-world implementation with a simpler implementation. A stub can replace full login system with a simple substitute. A stub’s job is to simulate the real world. Mocks are not stubs. A mock object, instead, is like a gauge that measures the way your application uses an interface.
  • Stubs provide canned answers to calls made during the test, usually not responding at all to anything outside what’s programmed in for the test. Stubs may also record information about calls, such as an email gateway stub that remembers the messages it ‘sent’, or maybe only how many messages it ‘sent’.
  • Mocks are what we are talking about here: objects pre-programmed with expectations which form a specification of the calls they are expected to receive.

Rspec Definitions for Mock and Stubs:Mocks are objects that allow you to set and verify expectations. They are very useful for specifying how the subject of the spec interacts with its collaborators. This approach is widely known as “interaction testing”.Mocks are also very powerful (though less widely understood) as a design tool. As you are driving the implementation of a given class, Mocks provide an amorphous collaborator that can change in behaviour as quickly as you can write an expectation in your spec. These changes are tantamount to designing the interface to a collaborator that often does not yet exist. As the shape of the class being specified becomes more clear, so do the requirements for its collaborators – often leading to the discovery of new types that are needed in your system.
Stubs are objects that allow you to set “stub” responses to messages. Stubs provide canned responses to messages they might receive in a test, while mocks allow you to specify and, subsquently, verify that certain messages should be received during the execution of a test.


Single Table Inheritance

Active Record allows inheritance by storing the name of the class in a column that by default is named “type” (can be changed by overwriting Base.inheritance_column). This means that an inheritance looking like this:

  class Company < ActiveRecord::Base; end
  class Firm < Company; end
  class Client < Company; end
  class PriorityClient < Client; end

When you do Firm.create(:name => “37signals”), this record will be saved in the companies table with type = “Firm”. You can then fetch this row again using Company.find(:first, “name = ‘37signals’”) and it will return a Firm object.

If you don‘t have a type column defined in your table, single-table inheritance won‘t be triggered. In that case, it‘ll work just like normal subclasses with no special magic for differentiating between them or reloading the right type with find.

Note, all the attributes for all the cases are kept in the same table. Another example is as follows:

Relational databases don’t support inheritance, so when mapping from objects to databases we have to consider how to represent our nice inheritance struc-tures in relational tables. When mapping to a relational database, we try to minimize the joins that can quickly mount up when processing an inheritance structure in multiple tables. Single Table Inheritance maps all fields of all classes of an inheritance structure into a single table.