Editing a form in nested_form gem

This is a very very naive and simple thing but I quite lost my time on this so I thought might be helpful.

Recently I was using the ‘nested_form’ gem by the great Ryan Bates (https://github.com/ryanb/nested_form). The form to create a new form works like a real gem without any effort.

Now, when I clicked on ‘edit’ link, it created some issues as the nested models didnt come.

I had a simple thing like each question has many answers. When I created a question, I added 5 answers to it but when I edited the question, no answers were visible.

The simple solution for this would be that the <% f.fields_for :answers do |an| %> line in your form would be without an equal to sign so just add it.

Thus, it looks like

<%= f.fields_for :answers do |an| %>

Thats all and it works like a charm!

Hope it helps.

Install apache web server and passenger on Ubuntu 11.04(Natty)

I just Installed apache and passenger on Ubuntu 11.04 to run and deploy my ruby on rails applications Passenger is a gem and can work with apache as well as nginx…

The reason for choosing apache is that its an industry standard.

Also one thing I did with apache was created virtual hosts and ran my apps on local machine with domains like http://www.application1.com

In this post I will list the steps I followed in order to setup apache web server and passenger.

Here is my stack:

  •  Ubuntu 11.04
  •  ruby 1.9.2 via rvm
  •  rubygems 1.8.10

I will be using rails 3.1.10(lastest this morning).!!

So lets start !!

  • Install rvm

To install rvm just type the following in the terminal(ctrl+alt+t)

 user$ bash < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer )

You can find more information about rvm on Here

  • Install ruby via rvm

Once rvm is installed you can install the latest or desired version of ruby by typing the following in terminal

rvm install 1.9.2

This will install ruby 1.9.2 on your system.

More information on how to make it your default ruby is available on here

  • Install rails.

just need to do

gem install rails

  • Install passenger

just do

gem install passenger

  • Install apache web server.

To install apache web server type:

sudo apt-get install apache2 apache2-mpm-prefork apache2-prefork-dev
  • Install passenger apache module.

Once this is done, we must install passenger , an apache module thats hepls us to rub rails apps on apache.

sudo passenger-install-apache2-module
  • Configure.

Finally everything is done.

When you run the passenger apache module, there would be some instructions that installer will give you.

The last thing it will tell is to paste some text in apache configuration file

The configuration file is located at /etc/apache2/apache2.conf

Now once this is done, we are ready to deploy.

This has a lot of information about deploying.

In my next post, I will show how to start rails apps on local machine with apache.

Hope it helps.!

Paperclip Resizing options…

Paperclip allows us to specify image dimensions in the  model iteself. This makes life very simple in cases where we only want image resizing.

Here is a list of things we can do to get the best out of it….

Please note : it applies to image magick also.

The basic specification is <width>x<height> in pixels, optionally followed by a modifier. In some cases you can omit either width or height.

    • 256×256
      This specifies the Maximum dimensions for the image, while preserving the aspect ratio of the image. So if your image were actually 512×256 it would be resized to 256×128 in order to fit inside the specified size.
    • 256×256!
      This specifies the Exact image size, so a 512×256 image would be changed into 256×256, losing the aspect ratio.
    • 256x
      This specifies the desired width of the target image, leaving the height to be set so as to preserve the aspect ratio.


    • x256
      This specifies the desired height of the target image, while preserving the aspect ratio.
    • 256×256^
      This specifies the Minimum size for the target image, so the resized image may be larger than these dimensions.
    • 256×256>
      This specifies that the image will be resized only if it is Larger than the dimensions.
    • 256×256<
      This specifies that the image will be resized only if it is Smaller than the dimensions.

Deploying with Pasenger and apache

Recently had come accross the task of deploying a rails application with apache and passenger.

I did everything as prescribed in the way I used to but for some reasons I was shown the directory listing of the application instead of application being executed.

The change I had taken from my conventional way of giving the paths to using symbolic links.

Finally i figured out the solution as an issue with passenger and the way it treats symlinks:


here is what you need to put between the <directory> tags to get stuff working:


PassengerResolveSymlinksInDocumentRoot on



Hope it helps !

Resizing the image without chaning its dimensions using paperclip


In a recent application, the need of the hour was to reduce the file size of an image without changing its dimensions.

Now, this can be acheived by reducing the quality of the image.

ImageMagick library has a “convvert” command which does exactly the same..

for eg(on the terrminal) : convert image1.jpg -quality 10 image2.jpg

image1.jpg—>original image

image2.jpg—->final image


According to the paperclip wiki there is a :quality parameter which is allowed.

I tried that but for some reasons , I was not able to get it running.

I also tried using :convert_options but it did not work too.


Thus , I wrote my own processor and got the stuff working. Here is the model and processor code :

#######Model code###########

class Passet < ActiveRecord::Base
attr_accessible :caption, :markup, :media_passet, :pcontent_id
has_attached_file :media_passet,
:styles => {
: original => {
:geometry => “256×256<”,
:processors => [:qresize]
belongs_to :pcontent


###################Processor code########################

make a file called qresize.rb in #{Rails.root}/lib/papaerclip_processors

The path is mentioned because this path is loaded automatically….

module Paperclip
# handles compression of image by reducing its quality
class Qresize < Processor
def initialize file, options = {}, attachment = nil
@format = File.extname(@file.path)
@basename = File.basename(@file.path, @format)
def make
src = @file
dst = Tempfile.new([@basename, @format])
parameters = []
parameters << “:source”
parameters << “-quality 10″
parameters << “:dest”
parameters = parameters.flatten.compact.join(” “).strip.squeeze(” “)
success = Paperclip.run(“convert”, parameters, :source => “#{File.expand_path(src.path)}[0]“, :dest => File.expand_path(dst.path))
rescue PaperclipCommandLineError => e
raise PaperclipError, “There was an error during the Size Reduction  for #{@basename}” if @whiny


This is a general code for image resizing and probably at this stage, we may not require to write a processor.

But the advantage of doing this is that we can extend this to do a lot more as and when requirement comes.

Also, we can handle our video and audio processing by this easily.

The other option is to pass a block(lambda or Proc) to :styles hash but I personally feel this is a much cleaner approach.


Hope it helps.

PreProcessing in Paperclip


If at all you want to do any kind of prepreocessing on attachments using paperclip then here is a simple(not wen i did it for the first time…) way of getting a TempFile object and doing whatever you want.

Here I set the size of image (actually reduce the original size into half)


class Passet < ActiveRecord::Base
attr_accessible :caption, :markup, :media_passet, :pcontent_id
has_attached_file :media_passet,
:styles => {

: original => {
:geometry => Proc.new { |instance| instance.set_size },
:quality => 10

belongs_to :pcontent

def set_size

ori_img =Paperclip::Geometry.from_file(self.media_passet.queued_for_write[:original].path)



Here I reduce the dimensions if the image and reduce the quality too.

This way, I can save a 1.1MB image as 39.2KB image,

It it what I required,and I hope this will give you a hint about your own application.


Hope it helps.

PS: there are many other(mayb elegant solutions) which can be found on paperclip github page whose link I have posted above.


Just installed a new precise pangolin and thought of giving rbenv a try….

So collected this with a bit of googling….

rbenv is a new lightweight Ruby version management tool built by Sam Stephenson(of 37signals and Prototype.js fame).

The established leader in the Ruby version management scene is RVM but rbenv is an interesting alternative if you want or need something significantly lighter with fewer features. Think of it as a bit like Sinatra and Rails. It’s not about which is the best, it’s about which is better for you and your current requirements.

What’s  rbenv?

Compared to RVM, rbenv is light. For example, it doesn’t include any mechanism to install Ruby implementations like RVM does. Its sole job is to manage multiple Ruby “environments” and it allows you to quickly switch between Ruby implementations either on a local directory or default ‘system-wide’ basis.

With rbenv, you install Ruby implementations manually or, if you prefer a little help, you can try ruby-build, another project of Sam’s that provides RVM esque recipes for installing seven popular Ruby implementation and version combos.

rbenv primarily works by creating ‘shim’ files in ~/.rbenv/shims which call up the correct version of files for each Ruby implementation behind the scenes. This means ~/.rbenv/shims will be in your path and there’s no threat of incompatibilities between libraries or systems like Bundler and rbenv.

The key thing to be aware of, however, is that if you install a gem that includes ‘binaries’ (or any generally available command line scripts), you need to run rbenv rehash so that rbenv can create the necessary shim files.


Firstly, it’s worth noting that by default rbenv is incompatible with RVM because RVM overrides the gem command with a function. This means to get the full rbenv experience you’ll need to do a rvm implode to wipe away your RVM installation or, at the least, remove/comment out the RVM loader line in your .bash_profile and/or .bashrc.

The installation instructions for rbenv are likely to change fast due to its youth, so I suggest the README. However, rbenv has just been made into a homebrew package on OS X, so if you’re a homebrew user (and if you’re not, check out my screencast), try:

brew update brew install rbenv rbenv rehash

And then add this line to your ~/.bash_profile or equivalent:

eval "$(rbenv init -)"

When you open a new shell now, you can run commands like rbenv and rbenv version to see what’s going on. rbenv versions should return nothing since you won’t have any rbenv-enabled Ruby installations yet, so move on to the next step..

Installing Implementations for rbenv

If you have ruby-build installed, getting, say, Ruby 1.9.2-p290 installed is easy:

ruby-build 1.9.2-p290 $HOME/.rbenv/versions/1.9.2-p290

If you prefer to download tarballs and do your own Ruby installs, however, you just need to set the directory prefix at the ./configure stage in most cases. For example:

./configure --prefix=$HOME/.rbenv/versions/1.9.2-p290

Once you’ve installed a new Ruby in this way, you need to run rbenv rehash in order for rbenv to create the ‘shim’ binaries necessary to make the correction version of Ruby available on the path at all times.

The RVM Splashback

In the interests of completeness, it’d be amiss to not mention the minor drama that kicked off on Twitter and Hacker News about rbenv’s release.

rbenv made its way on to Hacker News where, surprisingly, many people railed against RVM. This, coupled with a slightly antagonistic tone taken by rbenv’s README (which has now been taken away), led RVM’s maintainer Wayne E Seguin to vent some pressure on Twitter:

Sam quickly clarified his position:

Nonetheless, Wayne took a little time off, and a campaign to encourage donations to Wayne for his work on RVM was kicked off on Twitter (by Ryan Bates, I believe). The campaign went well, taking RVM’s donations from $7468 to $11370 (at time of writing), a jump of almost $4000 in a few days.

Part of the complaint made in rbenv’s README was about RVM’s “obnoxious” redefinition of the “cd” shell builtin. Essentially, RVM would create a new function which called “cd” but also took into account any .rvmrc files present in each directory so that it could change Ruby version automatically. While there was some validity to this concern, Ben Atkin took some time to write a blog post correcting some of the misinformation on this point.

In the end, however, all seems to be well, and Wayne is already making regular commits to the RVM project again just days later. Hopefully the outpouring of support from the Ruby community for RVM over the past couple of days has shown Wayne that RVM still has a significant user base, most of who aren’t going anywhere new anytime soon. If you want to help out, of course, you can still donate to the RVM Pledgie.


If you’re happy with RVM, there’s not much in rbenv to really leap to. It’s just a lighter and more modular way to achieve the basic functionality that RVM provides while missing out on a lot more (although you can use rbenv-gemset to get some basic gemset-like features).

If, however, you want something “lighter” than RVM, rbenv is certainly worth a look. Its approach feels cleaner and more transparent at a certain level, and if this is of utmost importance to you, you may prefer it.

I personally switched back to rvm coz I am getting openssl error which is tricky(ofcourse mybad!) and not able to get over it…

Rails and attr_*

There is a small gotcha in rails attr_accessible method in ruby.

  • If there are no attr_accessible attributes on a model it’s open, any attribute can be written with .update_attributes() or a similar mass-assignment function.
  • If there is even one attr_accessible the model is closed except for those attributes defined to be attr_accessible.

So there is an implicit toggle involved in attr_accessible as well as the actual desired functionality of allowing an attribute to be mass-assigned

Creating virtual hosts in apache in local machine

In this post I show how to create virtual hosts on apache and run multiple rails apps on your local machine with names like



In the previous post I had shown how to deploy rails apps on local machine with apache web server

My software stack:

  • Ubuntu 11.04
  • ruby 1.9.2 p290.
  • Rails 3.1.10
  • rubygems 1.8.10

Lets start!

First we have to enable virtual aliases on the Apache S

sudo a2enmod vhost_alias

Now I assume that the rails app is at the location:



We first create a virtual configuration file:

Tyep the following in terminal:

sudo gedit /etc/apache2/sites-available/mydomain

Copy the following settings to your file:


<VirtualHost *:80>
ServerAdmin webmaster@domain.com
ServerName my_rails_app.com
ServerAlias http://www.my_rails_app.com

DocumentRoot /home/username/Desktop/rails_apps/my_rails_app/public
<Directory />
Options FollowSymLinks
AllowOverride All
<Directory //home/username/Desktop/rails_apps/my_rails_app/public>
Options Indexes FollowSymLinks MultiViews
AllowOverride All
Order allow,deny
allow from all

ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/

<Directory “/usr/lib/cgi-bin”>

AllowOverride None

Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch

Order allow,deny

Allow from all



ErrorLog ${APACHE_LOG_DIR}/error.log


# Possible values include: debug, info, notice, warn, error, crit,

# alert, emerg.

LogLevel warn


CustomLog ${APACHE_LOG_DIR}/access.log combined


Alias /doc/ “/usr/share/doc/”

<Directory “/usr/share/doc/”>

Options Indexes MultiViews FollowSymLinks

AllowOverride None

Order deny,allow

Deny from all

Allow from ::1/128



Important to note here is to change ServerName as per your convinince and Directory to your public of rails app.

Once this is done,

type the following to open the hosts file:

 sudo gedit /etc/hosts


In this file, copy the following code: domain-name.com


replace domain name with your desired name.

This is what you will use in browser to access the page

Activate your domain and reload the Apache Server to enable settings
Enable the site

a2ensite domain-name


Reload Apache2

/etc/init.d/apache2 reload


Finally test your app by typing www.domain-name.com and see the magic !!!



Deploying rails app with apache locally

In this post I am going to show how to make apache the server for all ruby on rails application on local machine.

In the previous post I had shown how to install apache web server ad configure it.

My software stack:

  • Ubuntu 11.04
  • ruby 1.9.2 p290.
  • Rails 3.1.10
  • rubygems 1.8.10

Lets start!

I assume that you have a rails app in the following path:


It is important to note that apache serves all local request via www directory in /var.


So the first step is to create a symbolic link:

ln -s /home/username/Desktop/rails_apps/my_rails_app/public /var/www/my_rails_app

Note that sym link should be to your appls publc folder.

Now edit the following file(you can coly paste the code)

sudo gedit /etc/apache2/sites-available/default

In this file, append the follwing line:

RailsBaseURI /my_rails_app
RailsEnv development #(if you want to run on development mode default is production)

Restart apache using

sudo /etc/init.d/apache2 restart

 Now on you browser when you type
 the app should fire up !

Hurray you have done it !

————————————–warning for ruby 1.9.2p290————————————————

When I fired up my app, I got an error

Can’t convert nil to hash,

This is phsyc problem and to solve this, add the following to boot.rb

(this issue existed when I did used it )

require ‘yaml’

YAML::ENGINE.yamler = ‘syck’