May 01

In this article i have just taken a short example describing vertical table,and its implementation using rails.

When table has no fixed column it has dynamic fields .data is not stored on separate column but data stores in vertical fashion.

For implementing vertical table table has mainly 2 columns key and value pair.key is like database column name and value contains actual data.

Lets take an e.g

Consider website in which it contains various products and its comparison ,searching and many more features.product can be mobile,car etc.Product has many items.item may be nokia 6600,nokia n72 etc.

Here our aim is not compare aur search items.Here our main aim is how vertical table concept is applied.Suppose we have to build only single product comparison site then each product has it’s own attributes that can be easily build with adding column for each product.

we are developing generic site(multiple product).so there is no fixed attributes,each product has it’s own attributes either we create different model for each product or we can proceed with vertical table concept.

Vertical table

  • Product has many Product Attributes.
  • Product has many Items.
  • Item has many Item Attributes.
  • Item Attribute belongs to Product Attribute.

Product Attribute mainly requires 3 fields

name : which is used for key in vertical table(i.e column name)

option_type : which is used for viewing different form of data when item is created .(textbox,dropdown,checkbox,multi option)

option : which contain option if its drop down or multi option(serialize)

Item has only name field which is optional.

Item attribute mainly required 3 fields

name : key name or column name

value : actual value

item_id : foreign key of item

It is used where table has dynamic fields,and it only concern with data.

Here data grows vertically.

It has mainly key ,value pair.

Source code of above example is hosted on github http://github.com/amardaxini/vertical_table_demo

For More info about vertical table you can visit http://weblogs.foxite.com/andykramek/archive/2009/05/03/8369.aspx

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Feb 10

Static site using rails

As we know rails is mainly used for dynamic website.we can also display static web pages or we can deploy full static website using rails. The following code can help us to display static pages.

Step 1:-Create Rails project


rails static_site

Step 2:-Generate StaticPage Controller


ruby script/generate controller static_pages page

Step 3:- Create StaticPage Class in Model

 class StaticPage
   Formats = {
       "html" => "text/html",
       "png" => "image/png",
       "jpg" => "image/jpg"
     }
 end

Step 4:- Add following line in routes.rb


map.page "page/:filename.:format", :controller => 'static_pages', :action => 'page'

Here we are passing filename as parameter which is static file name.

This will generate url as http://sitename/page/static_filename.html

Step 5:- Now add following line into static_pages controller


def page
 send_file
 "#{Rails.root}/app/views/static_pages/#{params[:filename]}.#{params[:format]}",:disposition =>'inline',:type => StaticPage::Formats[params[:format]]
 end

Step 6:- All the static pages place in RAILS_ROOT/app/views/static_pages/ folder

Step 7 :- Start server and Type url as shown below.


ruby script/server

Url may be

http://railstech.com/page/contactus.html or
http://railstech.com/page/faq.html
Or In Development Mode
http://localhost:3000/page/faq.htm
http://localhost:3000/page/contactus.html

Feb 05

Today, I have started testing Beta release of Rails 3.0.By Default Rails 3.0 start with webrick.To start with mongrel do following steps.

1)Install mongrel gem


sudo gem install mongrel

2) After installing mongrel gem go to config/boot.rb file

and add following line

  require "mongrel"

3) Start server as rails server

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Jan 19

Rails Pdf Plugin act_as_flying_saucer

There are various ways to generate pdf documents in any language.In Rails we can use prawn library ,HtmlDoc,PrinceXml and many other library,using their api we can generate pdf document.Basically the primary goal is converting HTML web pages to PDF Document,without much changing existing CSS and HTML.

Using the Flying Saucer Project we can achieve this.we can convert HTML + CSS to PDF documents without much changing HTML and CSS. It also support CSS 2 and many properties of CSS 3 for printing Header,Footer,Page Number,Paginated Tables and many more.This Project is built on Java so Java is required on system.

Lets Start How to generate PDF Using Flying Saucer.

 script/plugin install git://github.com/amardaxini/acts_as_flying_saucer.git

This Plugin forked From

http://github.com/dagi3d/acts_as_flying_saucer

Which has older version of flying saucer project.

Next Step after installing plugin add flying_saucer.rb file at config/initializers.


ActsAsFlyingSaucer::Config.options = {
:java_bin => "/usr/bin/java",          # java binary
:classpath_separator => ':',  # classpath separator. unixes system use ':' and windows ';'
:tmp_path => "/tmp",          # path where temporary files will be stored
}

After Setting Java path , classpath separator and tmp path now do following step.

class PdfController < ActionController::Base
  acts_as_flying_saucer

  def generate_pdf
    render_pdf :template => 'pdf/pdf_template'
  end
end
  render_pdf :file=>'pdf/generate_pdf.html.erb'
  render_pdf :template=>'pdf/generate_pdf.pdf.erb',
             :send_file => { :filename => 'pdfdoc.pdf' }

Add act_as_flying_saucer to controller then render_pdf.There are various ways to render pdf using “template” or “file“,:send_file option use to send pdf file to client side.if we are using any external css file then this css shoulda have media option as ‘print’.


<%= stylesheet_link_tag 'pdf' ,:media=>'print' %>

If pdf containing images which generate on the fly.so instad of using

<%= image_tag %>

use

 <img src=" " >

Before rendering PDF validate HTML,like whether all tags are close properly or not.otherwise it gives an parse error.

Now You are ready to Generate PDF. Hurray!!!!!!!!!

How to generate Header, Footer,Page Number and Automation Of HTML Validation will be discussed in next post.

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Sep 17

Observer classes respond to lifecycle callbacks to implement trigger-like behavior outside the original class. This is a great way to reduce the clutter that normally comes when the model class is burdened with functionality that doesn‘t pertain to the core responsibility of the class.


In my project,I have to track certain action (create and update) of user on particular model basically i am maintaining some kind of log, or audit trails.In my application eventlog model has attribute user and body.


class EventlogObserver < ActiveRecord::Observer
  observe :model1, :model2

  def after_create(record)
    @eventlog = Eventlog.new
    @eventlog.body = record.class.to_S+“Created at”+Time.now
    @eventlog.save
    @event
  end
  def after_update(record)
    @eventlog = Eventlog.new
    @eventlog.body = record.class.to_S+“Updated at”+Time.now
    @eventlog.save
  end
end

This eventlog_observer.rb is stored in app/model

Now Configuration add following line in /config/environment.rb config.active_record.observers = :eventlog_observer

In rails there are various callbacks on which you trigger some common behaviour

  • after_create
  • after_update
  • after_save
  • after_destroy
  • before_create
  • before_update
  • before_save
  • before_destroy

and many more you can also refer from http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html

For further reference http://api.rubyonrails.org/classes/ActiveRecord/Observer.html

 
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Aug 19

In normal rails application contain one database,but if we want rails application having more than one database that is multiple data base.   we can achieve this using multiple way.one of the way is i am showing here.it’s just 3 steps.


Lets take an e.g Project has many milestone and milestone has many task

In normal scenario model looks like following way

 
class Project < ActiveRecord::Base 
  has_many :milestones 
end
 
class Milestone < ActiveRecord::Base 
  has_many :tasks 
 belongs_to :project 
end
 
class Task < ActiveRecord::Base 
  belongs_to :milestone 
end

Now  we want that milestone is stored on milestone_db database and task on task_db database
Rails multiple database

Now to achieve this we have to do the following steps

1) Edit Database.yml


 milestone_dev: 
 reconnect: false
 encoding: utf8 
 username: <user_name> 
 adapter: mysql 
 database: milestone_db 
 pool: 5 
 password: <password> 

task_dev: 
 reconnect: false 
 encoding: utf8 
 username: <user_name> 
 adapter: mysql 
 database: task_db 
 pool: 5 
 password: <password> 

Now create milestone_db and task_db database.


2) Edit milestone.rb and task.rb


class Milestone < ActiveRecord::Base 
  #add this line to use milestone_db 
  self.establish_connection :milestone_dev 
  has_many :tasks 
  belongs_to :project 
end 
 

class Task < ActiveRecord::Base 
  #add this line to use task_db 
  set_table_name "tasks" 
  belongs_to :milestone 
end

3) After editing model edit migration file


class CreateMilestones < ActiveRecord::Migration 
  def self.connection 
    Milestone.connection 
  end 
 .....
end

Now rails application is ready with multiple database.

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