Question

I have a simple user table and i would like to add a new field to my user table that says permalink. This permalink would be updated with the following code for all the users
name.downcase.gsub(/[^0-9a-z]+/, ' ').strip.gsub(' ', '-'). I want to create a migration file that updates all the users permalink fields with the code above so that old users would have their permalink set and i would use an after_create method for new users.

Answer 1

I think you could try something like this:

class User < ActiveRecord::Base

  before_create :set_permalink

  def set_permalink
    permalink = name.downcase.gsub(/[^0-9a-z]+/, ' ').strip.gsub(' ', '-') 
  end
end

This actually uses the before_create callback, which would address the deriving of the permalink field for new users. I think this is what you actually need.

And in your migration file …

class UpdateUsersPermalink < ActiveRecord::Migration

  def self.up
    User.reset_column_information
    User.all.each do |u|
      if u.permalink.nil?
        u.set_permalink
        u.save!
      end
    end
  end

  ...
end

.. which would take care of any existing Users that do not have this field set just yet.