ruby on rails add a column after a specific column name

问题

I tried to add a column to a table after a specific column in the table. Here is what I did:

rails generate migration add_reaction_id_to_patient_allergies reaction_id: integer :after => 'patient_id'

Here is what my migration file looks like:

class AddReactionIdToPatientAllergies < ActiveRecord::Migration
  def change
    add_column :patient_allergies, :reaction_id, :string
    add_column :patient_allergies, :integer, :string
    add_column :patient_allergies, :, :after
    add_column :patient_allergies, :=, :string
  end
end

I dont think the command went well. I see an '=' in the above file. I do not think it should be there. Can someone tell me if I missed anything?

If so , how do I undo the above?

回答1:

I doubt it allowed you to actually rake db:migrate this migration, so you shouldn't have to roll back. Just remove the bottom three add_columns and replace the top one with

add_column :patient_allergies, :reaction_id, :integer, after: :patient_id

and it should be fine to migrate. For future reference, here's what that command you entered should look like:

rails generate migration add_reaction_id_to_patient_allergies reaction_id:integer

The space before integer made the generator think it was a new column. Sadly you can't use Ruby syntax (a => b) on the command line either.

来源：https://stackoverflow.com/questions/15481733/ruby-on-rails-add-a-column-after-a-specific-column-name