Overriding class methods for migrations, a follow-up

October 16th, 2007

I realized I left one important point out from my previous post. I’m sure a few of you may have already picked up on this as well. When you override the class in the migration, you can add in whatever methods you would like the migration to use. We’ll use the same example as before:

004_add_live_pages.rb 

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class AddLivePages < ActiveRecord::Migration
  
  # Say for instance the Page.rb model has 20 instance methods in it
  # that we don't want to have affect our migration, but there is
  # 1 method we want to use below
  class Page < ActiveRecord::Base
  
    # The method 'stripped_name' below is an extension
    # of the String class
    def set_permalink
      self.update_attribute( :permalink, "#{self.id}-#{self.stripped_name}" ) if self.permalink.blank?
    end
  
  end
  
  def self.up  
    page = Page.create(
      :name => "About",
      :body => "Write your about page content here.",
    )
    page.set_permalink
  end
  
  def self.down
  end
  
end

Ta da! Now we can use the ‘set_permalink’ instance method anywhere inside our migration

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