0

In the new preferred way, there is only 1 method which seems to add a column. Does that mean you don't need to have a method to remove columns?

# the old way
class AddNameToPerson < ActiveRecord::Migration
  def up
    add_column :persons, :name, :string
  end

  def down
    remove_column :person, :name
  end
end

# the new prefered way
class AddNameToPerson < ActiveRecord::Migration
  def change
    add_column :persons, :name, :string
  end
end
Sam
  • 8,387
  • 19
  • 62
  • 97

2 Answers2

2

That's the magic of Rails 3.1 and later. Rails knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method.

Rails keep track of migration. So it will have the implementation for reverse the changes added by the migration when you roll back. Earlier we use to have two methods up and down. On Rails 3.1 and later they changed migration to have change method.

In case of add_coulmn reverse method is remove_column and same for other methods. Using tracked detail it will call appropriate action. So you don't need two methods(up and down). You can see the methods supported by change method: here. If you have other then these method you need to use up and down.

If you are confused with using change method then I suggest you to use up and down. Once you thorough with migration you can start using change method.

Rahul Tapali
  • 9,887
  • 7
  • 31
  • 44
1

You are right, You don't need a separate method to remove columns.

You can even try 'rake db:rollback' and then again 'rake db:migrate' if you don't have any data to lose.

It works perfectly. :)

Bot
  • 1,001
  • 2
  • 13
  • 32