How do I automatically assign a role to a user when my assignment is related to user model on a has_many through ? Rails 3

What I would like to do is when a user is created, it automatically gives them a role.

The thing is that the role is related to the user via an assignment table and a has_many through association.

The code is as follows:

User model


# == Schema Information
# Schema version: 20110214082231
#
# Table name: users
#
#  id                   :integer         not null, primary key
#  email                :string(255)
#  encrypted_password   :string(128)
#  password_salt        :string(255)
#  reset_password_token :string(255)
#  remember_token       :string(255)
#  remember_created_at  :datetime
#  sign_in_count        :integer
#  current_sign_in_at   :datetime
#  last_sign_in_at      :datetime
#  current_sign_in_ip   :string(255)
#  last_sign_in_ip      :string(255)
#  username             :string(255)
#  f_name               :string(255)
#  l_name               :string(255)
#  created_at           :datetime
#  updated_at           :datetime
#  invitation_token     :string(60)
#  invitation_sent_at   :datetime
#  plan_id              :integer
#  current_state       开发者_Python百科 :string(255)
#  confirmation_token   :string(255)
#  confirmed_at         :datetime
#  confirmation_sent_at :datetime
#

class User < ActiveRecord::Base
  before_create :assign

  has_many :assignments
  has_many :roles, :through => :assignments

  def role_symbols
    roles.map do |role|
      role.name.underscore.to_sym
    end
  end

  def assign
      @assignment.build_role(:user_id => self.id, :role_id => '3')
  end

end

Assignments model

# Table name: assignments
#
#  id         :integer         not null, primary key
#  user_id    :integer
#  role_id    :integer
#  created_at :datetime
#  updated_at :datetime
#

class Assignment < ActiveRecord::Base
    belongs_to :role
    belongs_to :user
end

Role model


# == Schema Information
# Schema version: 20101117094659
#
# Table name: roles
#
#  id         :integer         not null, primary key
#  name       :string(255)
#  created_at :datetime
#  updated_at :datetime
#

class Role < ActiveRecord::Base
    has_many :assignments
    has_many :users, :through => :assignments
end

---

Firstly, don't use hard-coded ids to find your roles as they may change.

Secondly, use association builders, or just access the roles association yourself.

Thirdly, follow the rule of "Don't Make Me Think" (DMMT) when naming your methods.

With these three things in mind:

def assign_default_role
  self.roles << Role.find_by_name("User")
end