Fix uninitialized constant error of existing migrations for deleted table (including model)

Question

I have a cars table which was created a year ago and needs to be renamed to vehicles table now.

Car table migration

class AddDataToCarsModel < ActiveRecord::Migration[5.0]
  def change
    # some cars are missing their created timestamp
    Car.where(created_at: nil).each do |car|
      date = Time.zone.now
      car.update_attribute(:created_at, date)
    end
  end
end

Vehicle table renaming migration

class RenameCarsToVehicles < ActiveRecord::Migration[5.1]
  def change
    rename_table :cars, :vehicles
  end
end

However, when dropping the current db and running the migration I get uninitialized constant AddDataToCarsModel::Car error as I have already removed the cars model as a part of it. What is a best practice for these situations? Is it worth running into old migration that was create a year ago and update it? How can we handle these situations?

Thanks for the help.

Answer 1

As a fix of your migration you could change your AddDataToCarsModel migration into this:

class AddDataToCarsModel < ActiveRecord::Migration[5.0]

  class Car < ActiveRecord::Base
    self.table_name = 'cars'
  end

  def change
    # some cars are missing their created timestamp
    Car.where(created_at: nil).each do |car|
      date = Time.zone.now
      car.update_attribute(:created_at, date)
    end
  end
end

So you can use Cars model only in this migration. And this will not break anything into your app lifecycle.