How do I reuse a previous migration's up or down methods

I had created my own User class and authentication from scratch but have recently decided to scrap it and start over using the Devise gem. So before I leverage the Devise migrations I need to create a migration to kill off my User table. "Easy", I thought, "I'll just use the down method of the migra开发者_运维技巧tion that created my User table". But I can't for the life of me work out how to reference that from a new migration. Thoughts?

If your user migration has anything outside of just dropping the user table I'm not too sure, but you can edit devise's migration and add the force = true option.

class DeviseCreateUsers < ActiveRecord::Migration
  def self.up
    create_table(:users, :force => true) do |t|
      ...
    end
  end
end

This will make it so that if your user table exists, it'll be dropped before hand.

You can just manually drop it:

class DropUsers < ActiveRecord::Migration
  def self.up
    drop_table :users
  end
  def self.down
    raise ActiveRecord::IrreversibleMigration
  end
end