Models look nice, but sometimes you just want to change they way they feel

mongodb | rails | ruby

MongoId models provide an excellent level of abstraction. Consider a User model.

class User
  include Mongoid::Document

  devise :invitable, :database_authenticatable, ...

  field :name, :type => String
  field :email, :type => String
end

We have derived an _Admin _type from it.

class Admin < User

end

This avoids having to have an explicit user type. In the database the distinction will be the _type field and correct objects are instantiated by querying auto-magically.

But how do we promote a User into an Admin?

We have to change the internal _type field. So far I found only one way, reach down to MongoDB and update the field explicitly.

def self.promote!(user)
    users = Mongoid.master.collection('users')
    users.update( { :"_id" => user.id }, { :"$set" => { :"_type" => "Admin" }})
end

I feel dirty. Is there a better way?