In many (most) cases, Rails can determine the relevant down
for a given
migration automatically, and you can simply write the change
method with
the code that would have gone in up
.
class AddAddressToUsers < ActiveRecord::Migration
def change
add_column :users, :address, :string
end
end
Check out the [Rails Guide to Migrations section on the Change Method][] for
the full list of automatically reversible migration methods.
[Rails Guide to Migrations section on the Change Method]: http://edgeguides.rubyonrails.org/active_record_migrations.html#using-the-change-method