Poetry of Programming

Its about Ruby on Rails – Kiran Soumya


Handling GIT Conflicts

I am attempting to push when I experience a conflict (ruby-1.9.2-p180)

cts_work/diaspora_cts git:(master)> git push origin master

To git@gitorious.org:diaspora_cts/diaspora_cts.git

 ! [rejected]        master -> master (non-fast-forward)

error: failed to push some refs to ‘git@gitorious.org:diaspora_cts/diaspora_cts.git’

To prevent you from losing history, non-fast-forward updates were rejected

Merge the remote changes (e.g. ‘git pull’) before pushing again.  See the

‘Note about fast-forwards’ section of ‘git push –help’ for details.


First, see if the conflict can be automatically resolved:

cts_work/diaspora_cts git:(master)> git pull

error: Your local changes to the following files would be overwritten by merge:


Please, commit your changes or stash them before you can merge.



Git status shows that your state is conflicted:

cts_work/diaspora_cts git:(master)> git status

# On branch master

# Your branch and ‘origin/master’ have diverged,

# and have 2 and 1 different commit(s) each, respectively.


nothing to commit (working directory clean)


IMPORTANT – If you can resolve the conflict do so (normal procedure), this procedure presumes you wish to write the conflicting updates to a branch.

Reset your tree to just your unmerged updates:

cts_work/diaspora_cts git:(master)> git reset –hard HEAD

HEAD is now at 340a54e changes amde


Create a branch, use a name which suggests a conflict:

cts_work/diaspora_cts git:(master)> git branch conflict_stuff

cts_work/diaspora_cts git:(master)> git branch


* master


Reset your tree to the prior revision:

cts_work/diaspora_cts git:(master)> git reset –hard HEAD

HEAD is now at 340a54e changes amde


Pull the other persons changes:(Do not do git pull but always git fetch + git merge)

cts_work/diaspora_cts git:(master)> git fetch

cts_work/diaspora_cts git:(master)> git merge origin/master

Merge made by recursive.

 app/controllers/sessions_controller.rb            |   21 ++++++—-

 app/models/profile.rb                             |    3 +-

 app/views/layouts/application.html.haml           |   14 +++—

 app/views/people/_profile_sidebar.html.haml       |   15 +++++–

 config/locales/diaspora/en.yml                    |    1 +

 db/migrate/20110226134747_add_columnto_profile.rb |    2 +

 db/schema.rb                                      |    5 ++-

 lib/tasks/profile_update.rake                     |   42 +++++++++++++++++++++

 public/javascripts/application.js                 |    2 +-

 9 files changed, 81 insertions(+), 24 deletions(-)

 create mode 100644 lib/tasks/profile_update.rake


Switch back to your branch:

cts_work/diaspora_cts git:(master)> git checkout conflict_stuff

Switched to branch ‘conflict_stuff’

cts_work/diaspora_cts git:(conflict_stuff)> git status

# On branch conflict_stuff

nothing to commit (working directory clean)


Push your conflict branch back to the repoistory:

cts_work/diaspora_cts git:(conflict_stuff)> git push origin master

Counting objects: 11, done.

Delta compression using up to 2 threads.

Compressing objects: 100% (8/8), done.

Writing objects: 100% (8/8), 861 bytes, done.

Total 8 (delta 5), reused 0 (delta 0)

=> Syncing Gitorious… [OK]

To git@gitorious.org:diaspora_cts/diaspora_cts.git

   d25e82a..c977122  master -> master


How Secured is your Rails App?

What do you prefer in terms of Authentication?

Plugin – Restful Authentication (recommended) – easy to use and you can tweak it according to your requirements.

Build your own authentication. You should rarely need to do this … Restful Authentication is quite flexible.

OpenID – a universal authentication system to avoid use of multiple username and password on the Internet. OpenID is getting quite famous now-a-days.

Access Control : To easily proivde different priviliges to your users. There are a lot of cool plugins available for access control.

Centralized Authentication Server – is used to implement single login/password for your users across multiple application. It can also be used for a single sign-on system. For example, Gmail and Google Reader have a single sign-on between them.

Use Google Authentication API to let your users login using their google username and password.

More Plugins :

Read More


Ubuntu 9.10 running in low-graphics mode

After the installation from update manager, and every time I boot up my machine, I get a error with three options out of which I am forced to click OK for “Run Ubuntu in low-graphics mode for just one session” option.

Resolution upon reference from url (http://ubuntuforums.org/archive/index.php/t-1242813.html) for Ubuntu 9.10:

Take a backup and edit xorg.conf file:

sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf_bkp
sudo gedit /etc/X11/xorg.conf

Delete this Section Device:

Section “Device”
Identifier     “Device0”
Driver         “nvidia”
VendorName     “NVIDIA Corporation”
BoardName      “GeForce 8400M GS”

And Edit the Section Screen as:

Section “Screen”
Identifier     “Screen0”
Device         “Device0”
Monitor        “Monitor0”
DefaultDepth    24
SubSection     “Display”
Depth       24
Modes “1440×990”

Here we go, no more low graphics mode issues.


Windows 7 and ROXIO

I recently got my XPS M1330 notebook upgraded from Windows Vista to Windows 7.It happened that one day I need to burn a CD and found that ROXIO DVD Creator is no more working though I have used it less. I have found the collection of CDs given by Dell and re-installed ROXIO Creator 9.  Thats it ! I made my own Axe on neck. Everytime I boot up my notebook. a pop up near the windows toolbar stating “This driver has got compaitibity issues with windows blah… blah…” and then the following errors appear:Microsoft Visual C++ Runtime LibraryRuntime Error!Program:…ommon Files\RoxioShare\9.0\SharedCom\(application).exeThe application has requested the Runtime to terminate it in an unusual way.Please contact the applications support team for more information – OR – Microsoft Visual C++ Runtime LibraryRuntime Error!Program: C:\Program Files\Roxio\(application folder)\(application name).exeR6025- pure virtual functional call I should say its more than a nightmare. This error keep popping up by freezing my notebook every 10-15 minutes approx. I tried all my ways of uninstalling it by following this support url of ROXIO.http://kb.roxio.com/search.aspx?URL=/content/kb/Creator/000127CR&PARAMS=But No Go !The error continued  for several Days..  Irritated and frustrated, today i just sat for hours to fix it. Finally I did it. Took almost 6 hours to google it and fix it though.I am blogging it to help another “Sufferer” of Roxio.Step 1:  I have got ROXIO installed as many Programs infact using the Roxio Creator 9 CD given by Dell.

  • “Roxio Audio”
  • “Roxio MyDVD”
  • “Roxio Drag and Disc” etc.. with update manager included.

Step 2: Instead of uninstalling the programs through Control Panel remove programs. Uninstall themFrom Program Files -> roxio XXX -> UninstallFollow this support url ->   http://kb.roxio.com/search.aspx?URL=/content/kb/Creator/000127CR&PARAMS= Step 3: I did everything but I couldnt delete Program Files -> Commom Files -> Roxio Shared/Sonic Shared.It says that it is used by some other application. Those are nothing but# RoxWatchTray9.exe# RoxMediaDB9.exe# VideoWave9.exe# MyDVD9.exe# MediaManager9.exe# DiscCopier9.exe# RXLabelCreator.exeStep 4:  I opened Task Manager in Windows 7 , it didn’t showed me any of these processes running. Here lies the main story. Due to which I couldnt delete the Roxio Shared under common files folder which is the root cause of Runtime error Popping up now and then.I even ran to buy Perfect uninstaller Software by reading this :http://www.squidoo.com/uninstallroxioI used that software and got ROXIO uninstalled though.Later I found “Show all process from all users” tab under Task Manager wherein you can end that process of roxioxxx.exe running and easily delete that Roxio shared folder under common files.Great ! those Perfect uninstaller people are earning on Roxio. Kudos to them! Kicks to roxio! and Sorries for other Users (like me)! But dont worry, just try the above steps.


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)


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…! :)


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..


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 !


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.


The “remembered” three fishes story…

Instead of using the word “unforgettable story”, I should say this story is always remembered in every act of my life.

The story is a lesson of my telugu detailed text book in my school days and it is … as follows:

Once upon a time, there lived three fishes in a lake. Their names are “Bhuddimathi”, “Kalamathi” and “Mandamathi”. I hope you got the story by names… But still let me continue… They used to live together and lead a happy undisturbed life in the lake. But one day suddenly… villains appeared… two fishermen… they were standing next to the lake and talking about fishing this place soon. They have decided to come with nets and other things the next week. The three fishes who heard this got scared… Bhuddimathi has decided to start to the next lake near by before those fishermen come. The next day early morning itself, it alerted the other two fishes and reached the other lake safely. The other two fishes thought there was lots of time left to them so they took it easy. Finally, the two fishermen approached the lake one day before they planned… Kalamathi as it is smart… acted dead once its caught. And thinking that fish was really dead .. the fisherman threwed it back to the lake. And it safely started its journey to other lake. But the third fish “Mandamathi” finally who could neither be like Bhuddimathi acting before nor like Kalamathi acting smart was fated to death due to its negligence.

So from then… in every work I do… my mom alerts me saying… be like Bhuddimathi study before itself or complete your work before itself… Even now… in anything… if I have to get fruits or if I have to get milk for curd or if I have to book my tickets to vizag or in anything.. this Kalamathi, Mandamathi and Bhuddimathi characters appear… Always I prove her to be Kalamathi but never Bhuddimathi…

But nowadays seriously… I improved from Kalamathi to Bhuddimathi… Believe me Mom!


Dilemma of a Developer under TL

I have a group of friends in big MNC software fields… who complain a lot about their Tls … almost every day… And I cant complain in return because I dont have one !!! Infact.. I am the Tl/owner of my own Task..

But when a developer works under someone or managed by someone… that someone becomes a Guru for the developer. As an Indian Slogan…”Guru Devo Bhava !” [which means “Guru is equal to God”].

But if there are too many Gurus…??? Simple… Too many Gods… :)
Taken Project on Hand… Incremental Developments or Releases are possible only when…

1> The manager knows… whos eligible for what… On a situation to give freedom to developers.. tasks decided within the group need to be known to everyone.

2> When you let the developer complete implementing his whole idea whatever he understands… after a ONE-TIME compulsory discussion/Goal achievement Plan — and thats perfect ! Because Guru is God !

3> Without completion of this one-time plan by the developer… never add new stuff/discussions that confuses the developer neither to complete his past work nor do the newly added stuff.

4> Any debates on the idea to be taken place only with the right person or the creator who knows everything.
5> The bottomline should surely be shared with the developer who ultimately needs to complete the goal.

6> Thereby the easy developer feels easy to release whatever on hand and every week meetings includes the happy releases whether it is accepted/rejected. This surely makes the track of the work and the developer.

7> Arguments/debates are allowed weekly once to change the plan or update it to make this another solid release.

8> A plan that changes daily is never said or called it as a “Plan”. If planning is perfect… then releases are perfect…

Hey Tls…! If you set the plan … then the developer is just a perfect mirror of your plans/ideas… or else leave everything to the developer… sometimes he knew better than you…!!!

Never blame the Developer rather believe… Because He gives Life for it as he is the one who builds it !!!


Pin Drop Sound please…

Code code code… hurray…
But whos that? calling me there…

Discussion Discussion Discussion…
Confusion Confusion Confusion…

Too many cooks… threw me in a hot pan…
Although… I have set my plan.

The whole concept… lost its fuse.
And who is this now … dumping things in dose.

What the heck the themes/dress change do
Please… Please give me a clue…

When not even the model/doll exists…
Help ! I need to complete this…

Ok say yes to one… say no to other…
Now see the fireworks around. do you bother?

Follow the right and make the domineer sad…
How to make all happy… without doing… all bad?

Wah! Finally… What a silence…
Now… I am leaving into the world of coding sense…

Me and my laptop…
On a rocket plane… to the success hill top !


So howzz Rails2.0? Its Awesome !

Added the “rake routes” task, which will list all the named routes created by routes.rb.

All resource-based controllers will be plural by default. This allows a single resource to be mapped in multiple contexts and still refer to the same controller. Example:
  # /avatars/45 => AvatarsController#show
  map.resources :avatars

  # /people/5/avatar => AvatarsController#show
  map.resources :people, :has_one => :avatar

Rendering a HTML page in Iphone using Rails 2.0 Multi View

Speaking of the iPhone, we’ve made it easier to declare “fake” types that are only used for internal routing. Like when you want a special HTML interface just for an iPhone. All it takes is something like this:
  # should go in config/initializers/mime_types.rb
  Mime.register_alias “text/html”, :iphone

  class ApplicationController < ActionController::Base
    before_filter :adjust_format_for_iphone

      def adjust_format_for_iphone
        if request.env[“HTTP_USER_AGENT”] && request.env[“HTTP_USER_AGENT”][/(iPhone|iPod)/]
          request.format = :iphone

  class PostsController < ApplicationController
    def index
      respond_to do |format|
        format.html   # renders index.html.erb
        format.iphone # renders index.iphone.erb
You’re encouraged to declare your own mime-type aliases in the config/initializers/mime_types.rb file. This file is included by default in all new applications.

No more overhead of Requesting a bazillion of Javscript/Stylesheet files

In Rails2.0, Using javascript_include_tag(:all, :cache => true) will turn public/javascripts/.js into a single public/javascripts/all.js file in production, while still keeping the files separate in development, so you can work iteratively without clearing the cache.

Speed your application !

In Rails2.0, If you set ActionController::Base.asset_host = “assets%d.example.com”, we’ll automatically distribute your asset calls (like image_tag) to asset1 through asset4. That allows the browser to open many more connections at a time and increases the perceived speed of your application.

Identify your Record url just by object !

Added a number of conventions for turning model classes into resource routes on the fly. Examples:
  # person is a Person object, which by convention will
  # be mapped to person_url for lookup
  link_to(person.name, person)

API authentication over SSL

It’s terribly simple to use. Here’s an example (there are more in ActionController::HttpAuthentication):
  class PostsController < ApplicationController
    USER_NAME, PASSWORD = “dhh”, “secret”

    before_filter :authenticate, :except => [ :index ]

    def index
      render :text => “Everyone can see me!”

    def edit
      render :text => “I’m only accessible if you know the password”

      def authenticate
        authenticate_or_request_with_http_basic do |user_name, password|
          user_name == USER_NAME && password == PASSWORD


A built-in mechanism for dealing with CRSF attacks. By including a special token in all forms and Ajax requests, you can guard from having requests made from outside of your application. All this is turned on by default in new Rails 2.0 applications and you can very easily turn it on in your existing applications using ActionController::Base.protect_from_forgery (see ActionController::RequestForgeryProtection for more).

Also made it easier to deal with XSS attacks while still allowing users to embed HTML in your pages. The old TextHelper#sanitize method has gone from a black list (very hard to keep secure) approach to a white list approach. If you’re already using sanitize, you’ll automatically be granted better protection. You can tweak the tags that are allowed by default with sanitize as well. See TextHelper#sanitize for details.

Finally, added support for HTTP only cookies. They are not yet supported by all browsers, but you can use them where they are.

Exception handling

Lots of common exceptions would do better to be rescued at a shared level rather than per action. This has always been possible by overwriting rescue_action_in_public, but then you had to roll out your own case statement and call super. Bah. So now we have a class level macro called rescue_from, which you can use to declaratively point certain exceptions to a given action. Example:

  class PostsController < ApplicationController
    rescue_from User::NotAuthorized, :with => :deny_access

      def deny_access

Cookie store sessions

The default session store in Rails 2.0 is now a cookie-based one. That means sessions are no longer stored on the file system or in the database, but kept by the client in a hashed form that can’t be forged. This makes it not only a lot faster than traditional session stores, but also makes it zero maintenance. There’s no cron job needed to clear out the sessions and your server won’t crash because you forgot and suddenly had 500K files in tmp/session.

This setup works great if you follow best practices and keep session usage to a minimum, such as the common case of just storing a user_id and a the flash. If, however, you are planning on storing the nuclear launch codes in the session, the default cookie store is a bad deal. While they can’t be forged (so is_admin = true is fine), their content can be seen. If that’s a problem for your application, you can always just switch back to one of the traditional session stores (but first investigate that requirement as a code smell).

New request profiler

The new request profiler that can follow an entire usage script and report on the aggregate findings. You use it like this:

  $ cat login_session.rb
  get_with_redirect ‘/’
  say “GET / => #{path}”
  post_with_redirect ‘/sessions’, :username => ‘john’, :password => ‘doe’
  say “POST /sessions => #{path}”
  $ ./script/performance/request -n 10 login_session.rb
And you get a thorough breakdown in HTML and text on where time was spent and you’ll have a good idea on where to look for speeding up the application.


Makes it even simpler to create Atom feeds using an enhanced Builder syntax. Simple example:

  # index.atom.builder:
  atom_feed do |feed|
    feed.title(“My great blog!”)

    for post in @posts
      feed.entry(post) do |entry|
        entry.content(post.body, :type => ‘html’)

        entry.author do |author|

Faster Performance

Active Record has seen a gazillion fixes and small tweaks, but it’s somewhat light on big new features. Something new that we have added, though, is a very simple Query Cache, which will recognize similar SQL calls from within the same request and return the cached result. This is especially nice for N+1 situations that might be hard to handle with :include or other mechanisms. Also drastically improved the performance of fixtures, which makes most test suites based on normal fixture use be 50-100% faster.

More efficient Migrations

create_table :people do |t|
  t.column, “account_id”,  :integer
  t.column, “first_name”,  :string, :null => false
  t.column, “last_name”,   :string, :null => false
  t.column, “description”, :text
  t.column, “created_at”,  :datetime
  t.column, “updated_at”,  :datetime
endNow you can write:

create_table :people do |t|
  t.integer :account_id
  t.string  :first_name, :last_name, :null => false
  t.text    :description

Clean up your environment

Before Rails 2.0, config/environment.rb files every where would be clogged with all sorts of one-off configuration details. Now you can gather those elements in self-contained files and put them under config/initializers and they’ll automatically be loaded. New Rails 2.0 applications ship with two examples in form of inflections.rb (for your own pluralization rules) and mime_types.rb (for your own mime types). This should ensure that you need to keep nothing but the default in config/environment.rb.

Easier plugin order

This can require that you load, say, acts_as_list before your own acts_as_extra_cool_list plugin in order for the latter to extend the former.

Before, this required that you named all your plugins in config.plugins. Major hassle when all you wanted to say was “I only care about acts_as_list being loaded before everything else”. Now you can do exactly that with config.plugins = [ :acts_as_list, :all ].


Notes on using fb:swf in FaceBook

In facebook groups or discussions… I saw plently of developers struggling to embed fb:swf using FBML.

An example for them to make their life easier :)

<fb:swf swfsrc=”SRC_URL” allowscriptaccess=”all”
bgcolor=”#ECECEC” id=”some_id” wmode=”transparent” SWLIVECONNECT=”true”
flashvars=”serverPath=http://dynamic_url?fbid=<%=uid%>&some_params=blahblah” height=”200″ width=”382″
imgsrc=”img_url_at_beginning” />

The other Common Wiki Notes for this to be noted:

  • Currently, Facebook requires Flash version 9.0.0 for all <fb:swf> tags.
  • Make sure that the flashvars parameter is all lowercase. Some sources of embedded links capitalize the V, which does not work on Facebook.
  • Currently, Facebook wraps the resultant Flash object in a <div> tag, so despite the fact that the embed/object tag is not block-level, consecutive <fb:swf> tags will appear one above the other instead of side-by-side.
  • To verify that your Flash object was loaded from a Facebook page, do the following. For security, this technique does not embed your secret key in your Flash app:
  1. Get all the parameters whose names start with fb_sig_. (Do not include the fb_sig parameter itself.) In Flex use Application.application.parameters to do this.
  2. Strip the fb_sig_ prefix from each, and make sure the keys are lowercase.
  3. Create a string of the form param1=value1param2=value2param3=value3, etc., sorted by the names (not the values) of the parameters. Note: Do not use ampersands between the parameters.
  4. Pass this string to your server, where your secret key is stored.
  5. On your server, append your application secret key to the string that was passed in. The following is returned: param1=value1param2=value2param3=value3myappsecret
  6. On your server, create an MD5 hash of this string.
  7. Return the MD5 hash from your server to your Flash object.
  8. In your Flash object, compare the returned hash with the fb_sig parameter that was passed in. If they are equal, then your Flash object was loaded by Facebook. (Or by someone who stole your secret key.)

While the above technique doesn’t embed your secret in the Flash object, what you’re doing is making a public Web service to sign parameter strings with your secret and then embedding its address in your Flash object. This is just as bad as publishing your secret key (except you do the MD5 computation for any malicious clients). What you want to do is send all the parameters to the Web server (including fb_sig) and have it verify the signature internally and respond with either OK or NOT_OK.