Adding Dynamic Roles to Users

20131208171336_create_roles.rb

# db/migrate/20131208171336_create_roles.rb
class CreateRoles < ActiveRecord::Migration
  def change
    create_table :roles do |t|
      t.string :name

      t.timestamps
    end
  end
end

20131208171457_add_role_id_to_users.rb

# db/migrate/20131208171457_add_role_id_to_users.rb

class AddRoleIdToUsers < ActiveRecord::Migration
  def change
    add_column :users, :role_id, :integer
  end
end

new.html.erb

# app/views/admin/users/new.html.erb

<%= # form_for ... %>

  <div class="field">
    <%= f.label :role_id %>
    <%= f.collection_select :role_id, Role.all, :id, :to_s %>
    <a data-action=add-role href="#">Add New</a>
  </div>
  

role.rb

# app/models/role.rb

class Role < ActiveRecord::Base
  # They don't really need to have_many :users, unless that is useful.
end

show.html.erb

# app/views/users/show.html.erb

<p>You are an <%= @user.role_name %></p>

user_form.js.coffee

UserForm = do ->
  initialize = ->
    $('[data-action=add-role]').on 'click', -> addRole()

  addRole = ->
    # Here you can hide the select box and show a text
    # field, then have the user model accept that text
    # field and create a role before save.
    #
    # Another thing you could do is provide a little
    # modal that allows them to type in a role name,
    # perform an AJAX request to save that role, and
    # add that role to the select box with it automatically
    # selected.
    #
    # Or of course, you could also have a separate UI
    # for managing roles.

  return {
    initialize: initialize
    addRole: addRole
  }

UserForm.initialize()

your_user_model.rb

# app/models/your_user_model.rb

class YourUserModel < ActiveRecord::Base
  belongs_to :role
  
  # This will allow you to call "user.role_name" and retrieve
  # the role without it raising an exception if the associated
  # object does not exist.
  #
  delegate :name, to: :role, prefix: true, allow_nil: :true

end