Saari Development

Ali Rizvi's Technical Blog as a Professional Software Development Engineer

Archive for the ‘rails’ Category

Rails: Non-DB field in Model with validation

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Challenge: Add a field to the model representing system date, time & timezone that is not stored in the database and have validation on it.


  • Add attr_accessor & attr_accessible (for bulk update), add getter (sys_date_time) & setter (sys_date_time=) methods.
  • Return system date time in UTC from getter and show in user (browser) timezone on client side (using moment-timezone.js which is moment.js extension select the download with timezone data)
  • When the setting come to be saved using update_attributes in controller it eventually calls model setter (sys_date_time=) where you convert it back to utc given the timezone info (ActiveSupport::Timezone[zone] is your friend with ActiveSupport::TimeZone[zone].parse then in_time_zone(‘UTC’))
  • Validation is tricky as this is not a db backed and getter returns the calculated value which is always valid. You need to validate input first thing in setter and set a new member variable with errors found. Then add a validate do … end block where you iterate through the new member variable with errors and do errors.add(attr, message).

Will add code snippets when time permits.


Written by imsaar

April 7, 2016 at 2:02 pm

Posted in code, rails, ruby

Rails: Skipping Base Class Filters in Subclasses

with 3 comments

I encountered a case where we needed to skip a filter as it was causing infinite redirection in a subclass. I found my answer in: Rails Filters Documentation

Filter chain skipping

Declaring a filter on a base class conveniently applies to its subclasses, but sometimes a subclass should skip some of its superclass’ filters:

  class ApplicationController < ActionController::Base
    before_filter :authenticate
    around_filter :catch_exceptions

  class WeblogController < ApplicationController
    # Will run the :authenticate and :catch_exceptions filters.

  class SignupController < ApplicationController
    # Skip :authenticate, run :catch_exceptions.
    skip_before_filter :authenticate

  class ProjectsController < ApplicationController
    # Skip :catch_exceptions, run :authenticate.
    skip_filter :catch_exceptions

  class ClientsController  :index

Written by imsaar

November 10, 2009 at 9:07 pm

Posted in code, documentation, rails, ruby

MySQL and Rails: mysql.sock not found

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I started doing my webapp on my brand new server (ubuntu linux 7.04) and when trying to run my first migration I got the following error message:

rake db:migrate
(in /home/rizvi/projects/somewebapp)
rake aborted!
No such file or directory - /tmp/mysql.sock

Here is a useful mysql command to find out mysql defaults:

mysqladmin --print-defaults
mysqladmin would have been started with the following arguments:
--port=3306 --socket=/var/run/mysqld/mysqld.sock

Here is what solved the problem:

sudo apt-get install libmysql-ruby

Note: The above is an alternative to :

sudo gem install mysql

Now I get:

rake db:migrate
(in /home/rizvi/projects/somewebapp)
rake aborted!
Unknown database 'somewebapp_development'
(See full trace by running task with --trace)

So I need to do the following:

mysqladmin -u root create somewebapp_development -p
mysqladmin -u root create somewebapp_test -p
mysqladmin -u root create somewebapp_production -p

Reference: RailsOnUbuntu

Written by imsaar

August 6, 2007 at 6:37 am

Posted in mysql, rails