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I am trying to add one column in one table using migration up. I have created migration for that and ran rake db:migrate:up[version] it added the column in my table but I don't see that attribute in my respective model. Am I missing something here to do? Below is my snippet ...

migration 6, :add_role_users do
  up do
    execute <<-SQL
      ALTER TABLE users
        ADD COLUMN role varchar(32) DEFAULT NULL
    SQL
  end
  down do
    execute <<-SQL
      ALTER TABLE users
        DROP COLUMN role
    SQL
  end
end

After running the above migration I don't see below line in my User model 

property :role, , String, :length => 32

Please suggest, I am using Rails 3.0 so I can't use migration Change method.

Ben Lee
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user1653027
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    I don't understand what you expect the migration to do to your user model? It shouldn't affect it directly at all, all it does is add the database column. Also, why are you using raw sql in the migration instead of the simple rails helpers? – Ben Lee Oct 18 '12 at 22:20

1 Answers1

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Rails automatically detects and assigns model attributes based on your table's columns. For some generic information about how this is done, this guide is invaluable: http://guides.rubyonrails.org/migrations.html

Anyway, here's how I would run a migration that adds a role column to the users table.

  1. In your console, run rails g migration add_role_column_to_users role:string. (Since the migration name ends with "users", Rails will automatically know to apply this migration to the users table. Specifying role:string is just a command line shortcut that automatically adds t.add_column :role, :string to your migration. After running this command you should be able to find your new migration in the db/migrate/ directory of your app.)

  2. In your console, run rake db:migrate to migrate the database to your new schema.

  3. That's it! You should now have a "role" column on your "users" table. You can verify this by entering your Rails console with rails c, and bringing up your user model's column names with User.column_names. You should see "role" there.

alexpls
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  • Whoops, sorry I didn't realize that you were using Rails 3.0. This answer will probably only work with Rails 3.1+ – alexpls Oct 18 '12 at 22:29
  • Yeah, I am using 3.0 and I tried the above process, it won't work for 3.0, so is there any method we have that will update the Model automatically with migration itself like how it works with Rails 3.1+ without changing the model manually – user1653027 Oct 19 '12 at 14:54