Use of Dirty Objects

Uses of Dirty Objects

Developer have some confusion that how they can get the previous value of the field after update.
So here the rails has a way called Dirty objects.

You can found Module Dirty in rails/activerecord/lib/active_record/dirty.rb
This is just for track unsaved attribute changes.
There are few methods in dirty module as below
* Changed
* Changed?
* Changes
* Included
And it has some constants

DIRTY_SUFFIXES = ['_changed?', '_change', '_will_change!', '_was']

book = Book.find(1)

book.name = 'agiles'
book.changed? # => true
book.name_changed? # => true
book.name_was # => 'rails startup'
book.name_change # => ['rails startup', 'agiles']
book.name = 'agiles with rails'
book.name_change # => ['rails startup', 'agiles with rails']

You can found the details in http://api.rubyonrails.org/classes/ActiveRecord/Dirty.html

Remove .svn files / folders

I have found from some where to use the below syntax for remove .svn folders. And it works for me so i thought it might be useful. So i shared this

find ./ -name ".svn" | xargs rm -Rf

or

find ./ -name “.svn” -exec rm -rf {} \;

Source: http://www.rickhurst.co.uk/category/linux/

Receive Mail with attachment using TMail - Ruby on Rails

Receive Mails using TMail. I like to use TMail for receive mail because TMail is best to handle the header of the email object. There are only a few methods that deal directly with the body of the email. So i just thought to share it. I have used pop3 for receive mail and use TMail for parse it.
For use TMail you need to do install gem.

gem install TMail

def popmail
     require 'net/pop'
     require 'tmail_mail_extension.rb'

     pop = Net::POP3.new 'mail.example.com'
     pop.start 'test-receive@example.com', 'password'

     if pop.mails.empty?
       puts 'No mail.'
     else
       pop.each_mail do |mail|
        email = TMail::Mail.parse(mail.pop)
        subject = email.subject
        from_email = email.from
        body = email.body_html
        if email.has_attachments?
        email.parts.each_with_index do |part, index|
          filename = part_filename(part)
          content_type = part.content_type
          filename ||= "#{index}.#{ext(part)}"
          file = filename
          fname = file.split(".")
          newfilename = fname[0]+'_'+(Time.now.to_i).to_s+'.'+fname[1]
          filepath = "#{RAILS_ROOT}/public/file_attachement/#{newfilename}"
          File.open(filepath,'wb'){|f| f.write(part.body)}
          filesize= File.size(filepath)
        end
      end
       # Do your Logic after getting details
     mail.delete
     end
   pop.finish
end

def part_filename(part)
     file_name = (part['content-location'] &&
     part['content-location'].body) ||
     part.sub_header("content-type", "name") ||
     part.sub_header("content-disposition", "filename")
end

CTYPE_TO_EXT = {
     'image/jpeg' => 'jpg',
     'image/gif' => 'gif',
     'image/png' => 'png',
     'image/tiff' => 'tif'
}

def ext( mail )
     CTYPE_TO_EXT[mail.content_type] || 'txt'
end

Note: You can get body part of email by email.body and no need to use of tmail_mail_extension.rb

But it gives your body part two times. one in normal text of body and second is html of the same body. If you want only html of the body then you need tmail_mail_extension.rb. I found that logic of tmail_mail_extension.rb file from somewhere, i forgot the link for that.
But you can write below which i found from somewhere. Write below code in tmail_mail_extention.rb


tmail_mail_extention.rb
module TMail
   class Mail

   # returs an String with just the html part of the body
   # or nil if there is not any html part

   def body_html
     result = nil
     if multipart?
       parts.each do |part|
         if part.multipart?
          part.parts.each do |part2|
          result = part2.unquoted_body if part2.content_type =~ /html/i
          end
         elsif !attachment?(part)
          result = part.unquoted_body if part.content_type =~ /html/i
         end
       end
     else
       result = unquoted_body if content_type =~ /html/i
     end
     result
   end

   def parts_observer
     puts "INI"
     puts "content_type: #{content_type}"
     puts "body: #{body}"
     puts "parts.size: #{parts.size}"

     if multipart?
       parts.each_with_index do |part, index|
       puts ""
       puts " parts[#{index}]"
       puts " content_type: #{part.content_type}"
       puts " multipart? #{part.multipart?}"

       header = part["content-type"]

       if part.multipart?
         puts " --multipartt--"
         part.parts.each_with_index do |part2, index2|
          puts " part[#{index}][#{index2}]"
          puts " content_type: #{part2.content_type}"
          puts " body: #{part2.unquoted_body}"
         end
       elsif header.nil?
         puts " --header nil--"
     elsif !attachment?(part)
       puts " --no multipart, no header nil, no attachment--"
       puts " content_type: #{part.content_type}"
       puts " body: #{part.unquoted_body}"
     else
       puts " --no multipart, no header nil, attachment--"
       puts " content_type: #{part.content_type}"
     end

     end
     else
       puts " --no multipart--"
       puts " content_type: #{content_type}"
       puts " body: #{unquoted_body}"
     end

     puts "END"
   end

   end
end

Merb gets merged into Rails 3.0 !!

Ruby on Rails team broke the news: the alternative Ruby web application framework, Merb, will be merged into Ruby on Rails 3.0.

Merb, which was already closely patterned after Rails, brings performance, modularity, and better integration with alternative JavaScript and ORM frameworks to the table. The default Rails configuration will still be the "full stack" framework, which uses ActiveRecord and Prototype, but there will also be a "Rails Core" with the ability to opt into specific other (e.g. JavaScript or ORM) frameworks as desired.

The Merb team will be working with the Rails core team on a joint project. The plan is to merge in the things that made Merb different. This will make it possible to use Rails 3 for the same sorts of use-cases that were compelling for Merb users. Effectively, Merb 2 is Rails 3.

You can read more about here:

• http://weblog.rubyonrails.org/2008/12/23/merb-gets-merged-into-rails-3
• http://rubyonrails.org/merb
• http://yehudakatz.com/2008/12/23/rails-and-merb-merge/
• http://brainspl.at/articles/2008/12/23/merb-is-rails
• http://merbist.com/2008/12/23/rails-and-merb-merge/
• http://onrails.org/articles/2008/12/24/the-future-of-rails-rails-3-0
  

Inline file upload - iframe - ajax - Ruby on Rails

In View

<% form_for(@images, :url => formatted_images_path(:format => 'js'), :html => { :multipart => true,:target => 'upload_frame' }) do |f| %>
Image
<%= f.file_field :uploaded_data, :size => "50" %>
<%= f.submit :Submit %>
<% end %>
< id="'upload_frame'," name="upload_frame" style="width:1px;height:1px;border:0px" src = "about:blank">

in controller
def create
@image = Image.new
if @image.save
respond_to do |format|
format.js do
responds_to_parent do
render :update do |page|
page.replace_html 'imgupload', :partial => 'imageupload',:object => @images
page.visual_effect :highlight, "image_#{@image.id}"
end
end
end
end
end
end

Watermarking an image in Rails - Rmagick

class Image < ActiveRecord::Base

require 'RMagick'
has_attachment :content_type => :image,
:storage => :file_system,
:max_size => 4.megabytes,
:resize_to => '640x400>',
:thumbnails => { :thumb => '100x100>',:medium => '250x150' }

validates_as_attachment

def watermark_image
dst = Magick::Image.read("#{RAILS_ROOT}/public/#{self.public_filename}").first
src = Magick::Image.read("#{RAILS_ROOT}/public/images/logo.gif").first
result = dst.composite(src, Magick::CenterGravity, Magick::HardLightCompositeOp)
result.write("#{RAILS_ROOT}/public/#{self.public_filename}")
end

Improving Rails Applications performance

I have done some research about improving Rails Applications performance. I would feel the the following few points need to be considered when we optimize rails applications for performance:

1) Avoid the use of dynamic URL generation (link_to, url_for) since rails needs to look up the routes table and that may take time. Just hard code the controller name and the action.

2) Try to avoid the excess use of helpers since it adds overhead.

3) You may consider to use Rails Bench to do some testing for you rails application performance.

4) You may consider to use memcached to cache your model and library computation results.

5) try to optimize your database queries. If you use ActiveRecord find, be careful from computation intensive sql queries that returns to you a lot of data that you may not need. The method find may run many select statements for you.