Comma separated value not being stored - ruby-on-rails

Question

I have a model called org and department. Whenever a organization sign up, it must create a list of departments it has by entering the name of departments as comma separated value. The department list can also be edited later. These are my models:
0rg
class Org < ActiveRecord::Base
has_many :departments, dependent: :destroy
attr_accessible :name, :website, :department_list
validates :name, presence: true
validates :website, presence: true
def department_list
departments.collect { |d| d.department_name }.join(', ')
end
def department_list=(text)
if id && text
departments.destroy_all
text.split(',').each do |d|
departments.create(department_name: d.strip.capitalize)
end
end
end
end
Department
class Department < ActiveRecord::Base
attr_accessible :department_name, :org_id
belongs_to :org
end
My view
<%= f.text_area :department_list, :cols => "10", :rows => "10" %>
Problem:
When the organization sign up by entering the department name as comma separated value, it is not stored in the database. But when the organization updates the field later by edit action, only then department name is stored and it can be further edited at any time. I want the department name to be stored when organization sign up.
Please Help.
EDIT:
My Registration Controller:
class Webs::RegistrationsController < Devise::RegistrationsController
prepend_before_filter :require_no_authentication, :only => [ :new, :create, :cancel ]
prepend_before_filter :authenticate_scope!, :only => [:edit, :update, :destroy]
# GET /resource/sign_up
def new
build_resource({})
respond_with self.resource
end
# POST /resource
def create
build_resource(sign_up_params)
# customized code begin
# create a new child instance depending on the given user type
child_class = params[:web][:user_type].camelize.constantize
resource.role = child_class.new(params[child_class.to_s.underscore.to_sym])
# first check if child instance is valid
# cause if so and the parent instance is valid as well
# it's all being saved at once
valid = resource.valid?
valid = resource.role.valid? && valid
# customized code end
if valid && resource.save
if resource.active_for_authentication?
set_flash_message :notice, :signed_up if is_navigational_format?
sign_up(resource_name, resource)
respond_with resource, :location => after_sign_up_path_for(resource)
else
set_flash_message :notice, :"signed_up_but_#{resource.inactive_message}" if is_navigational_format?
expire_session_data_after_sign_in!
respond_with resource, :location => after_inactive_sign_up_path_for(resource)
end
else
clean_up_passwords resource
render :new
end
end
# GET /resource/edit
def edit
render :edit
end
# PUT /resource
# We need to use a copy of the resource because we don't want to change
# the current user in place.
def update
self.resource = resource_class.to_adapter.get!(send(:"current_#{resource_name}").to_key)
prev_unconfirmed_email = resource.unconfirmed_email if resource.respond_to?(:unconfirmed_email)
if resource.update_with_password(account_update_params)
resource.role.update_attributes(params[:org])
resource.role.update_attributes(params[:user])
if is_navigational_format?
flash_key = update_needs_confirmation?(resource, prev_unconfirmed_email) ?
:update_needs_confirmation : :updated
set_flash_message :notice, flash_key
end
sign_in resource_name, resource, :bypass => true
respond_with resource, :location => after_update_path_for(resource)
else
clean_up_passwords resource
render :edit
end
end
end