Question

So assume I have used rails generate to create a model and subsequently it created migrations for it.

Now it turns out I made a couple of modifications to those models (fixed up some relations). Is it possible to create migrations based off of my current model?

• I don’t want to use rails generate to generate the model again.
• I don’t want to manually write a migration.

Answer 1

What do you need to do with that migration?

If you need to remove or add some columns, you could use:
AddXXXToYYY and
RemoveXXXFromYYY.

So if you want to add a certain column to YYY table use:

rails generate migration add_attr1_and_attr2_to dogs attr1:string attr2:string

This would generate (rails 3.2.0):

class AddAttr1AndAttr2ToDogs < ActiveRecord::Migration
  def change
    add_column :dogs, :attr1, :string

    add_column :dogs, :attr2, :string

  end
end

Same goes for removing the columns:

r g migration remove_attr1_and_attr2_from_dogs attr1:string attr2:string