Add a role to the User Model

Set up the Role and User models

First create the Role model and link it to the User Model

$ rails g model Role name:string
$ rails g migration addRoleIdToUser role:references
$ rake db:migrate

Then in your Models

class User < ActiveRecord::Base
  belongs_to :role
end
class Role < ActiveRecord::Base
  has_many :users
end

Set up seeds.rb with your roles

['registered', 'banned', 'moderator', 'admin'].each do |role|
  Role.find_or_create_by({name: role})
end

Then

$ rake db:seed

Set up the default role as a model callback

class User < ActiveRecord::Base
  belongs_to :role
  before_create :set_default_role
  # or 
  # before_validation :set_default_role 

  private
  def set_default_role
    self.role ||= Role.find_by_name('registered')
  end
end