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This Tip Of The Day (TOTD) explains how to add pagination to your Rails application.

1. Create a simple Rails scaffold as:

   ~/samples/jruby >~/tools/jruby/bin/jruby -S rails paginate ~/samples/jruby/paginate >~/tools/jruby/bin/jruby script/generate scaffold book title:string author:string ~/samples/jruby/paginate >sed s/’adapter: sqlite3′/’adapter: jdbcsqlite3′/ <config/database.yml >config/database.yml.new ~/samples/jruby/paginate >mv config/database.yml.new config/database.yml ~/samples/jruby/paginate >~/tools/jruby/bin/jruby -S rake db:migrate

2. Edit “test/fixtures/books.yml” and specify the content as:
   

   # Read about fixtures at http://ar.rubyonrails.org/classes/Fixtures.html one:   title: Ultramarathon Man Confessions of an All-Night Runner   author: Dean Karnazes two:   title: My Life on the Run   author: Bart Yasso three:   title: 50/50 Secrets I Learned Running 50 Marathons in 50 Days   author: Dean Karnazes four:   title: Born to Run   author: Christopher Mcdougall five:   title: Four Months to a Four-hour Marathon   author: Dave Kuehls six:   title:  Galloway’s Book on Running   author: Jeff Galloway seven:   title: Marathoning for Mortals   author: John Bingham and Jenny Hadfield eight:   title:  Marathon You Can Do It!   author: Jeff Galloway nine:   title: Marathon The Ultimate Training Guide   author: Hal Higdon ten:   title: Running for Mortals   author: John Bingham and Jenny Hadfield

   and load the fixtures as:

   ~/samples/jruby/paginate >~/tools/jruby/bin/jruby -S rake db:fixtures:load (in /Users/arungupta/samples/jruby/paginate)

3. Run the application as:
   

   ~/samples/jruby/paginate >~/tools/jruby/bin/jruby -S glassfish -l Starting GlassFish server at: 129.145.132.8:3000 in development environment… Writing log messages to: /Users/arungupta/samples/jruby/paginate/log/development.log. . . . Jul 29, 2009 2:06:44 PM com.sun.grizzly.scripting.pool.DynamicPool$1 run INFO: New instance created in 7,488 milliseconds

   The application is accessible at “http://localhost:3000/books” and looks like:

   

   The page shows 10 rows, all in one page.

4. Lets add pagination to this simple sample.
1. Install will_paginate gem as:

   /tools/jruby >./bin/jruby -S gem install will_paginate JRuby limited openssl loaded. gem install jruby-openssl for full support. http://wiki.jruby.org/wiki/JRuby_Builtin_OpenSSL Successfully installed will_paginate-2.2.2 1 gem installed Installing ri documentation for will_paginate-2.2.2… Installing RDoc documentation for will_paginate-2.2.2…

   There are other methods of installation as well.

2. Edit “config/environment.rb” and add
   

   require “will_paginate”

   as the last line.

3. Edit the “index” action in “app/controllers/books_controller.rb” as:
   

   @books = Book.paginate(:page => params[:page], :per_page => 5) #@books = Book.all

   “:per_page” specifies the number of items to be displayed in each page.

4. In “app/views/books/index.html.erb”, add:
   

   <%= will_paginate @books %>

   right after “</table>”.

   The output now looks like:

   

   and clicking on “Next” shows:

   

   The information is nicely split amongst 2 pages.

An important point to remember is that will_paginate only adds pagination to your Rails app. You are still required to display all the values.

But essentially replacing “@books = Book.all” with “@books = Book.paginate(:page => params[:page], :per_page => 5)” in the Controller and adding
“<%= will_paginate @books %>” did the trick for us.

Clean and simple!

Please leave suggestions on other TOTD (Tip Of The Day) that you’d like to see. A complete archive of all the tips is available here.

Technorati: jruby rubyonrails glassfish pagination will_paginate

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