Forum: Ruby on Rails Rails 3 How to assign the value to nested attributes before calling save in update action

I am using Rails 3.0.9 and Ruby 1.9.2

Models associations are

document.rb
    has_many :sections
    accepts_nested_attributes_for :sections, :allow_destroy => :true,
:reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } }

section.rb
    belongs_to :document
    has_many :paragraphs, :dependent => :destroy
    has_many :contents :through => :paragraphs
    validates :user_id, :presence =>  { :message => "Must be filled" }

paragraph.rb
    attr_accessible :user_id, :section_id, :content_id
    belongs_to :section
    belongs_to :content
    validates :user_id, :section, :content, :presence =>  { :message =>
"Must be filled" }

paragraphs table just like a intermediate table for sections and 
contents
and I want to save records in documents, sections and paragraphs table
using single form submission.

_form.html.erb

    <%= form_for @document, :validate => true do |f| %>
    <%= f.error_messages %>
    <div><%= f.text_field :name %></div>

    <% f.fields_for :sections do |builder| %>
    <div><%= builder.text_field :name %></div>
    <div><%= builder.select :content_ids, Content.all.collect {|p| [
p.name, p.id ] },{:prompt => "Please Select"}, {:class => "nhs_select",
:multiple => true}  %></div>
        <% end %>
        <%= f.submit :submit%>
   <% end %>


Example parameters when submiting the form
    {"document"=>{"name"=>"sdf",
"sections_attributes"=>{"0"=>{"name"=>"sdf", "description"=>"sdf",
"_destroy"=>"0", "content_ids" => ["1", "2"]}}, "commit"=>"Create 
Document"}

In additionally, I should need to update current_user's id to user_id
column of paragraphs table.

def create
    @document = Document.new
    @document.attributes = params[:document]
    @document.sections.each {|section|
      section.user_id = current_user.id
      section.paragraphs.each {|paragraph| paragraph.user_id =
current_user.id}
    }
    if @document.save!
      # success
    else
      render :action => 'new'
    end
end

*Problem 1:*

At first, I submit the form, rails render new form without error message
even I have implemented code to display error messages.

then again clicked submit button, action goes to update method. But it
should go to new action.

I inspected in console, the inserted records were rollbacked but still 
the
ID is retain in object.

Example: <form id="edit_document_6" class="edit_document" method="post"
action="/documents/6" accept-charset="UTF-8">

*Problem 2:*

Documentation said that the changes are not saved to the database when
assigning the attributes as like user.attributes = {:name => Rob}.

but my case validation is triggered when assigning the attributes so I
can't assign the value to user_id column in paragraph object before 
calling
save method

@document.attributes = {"sections_attributes"=>{"0"=>{"name"=>"sdf",
"content_ids" => ["1", "2"]}}
or
section = Section.first
section.attributes = {"content_ids" => ["1", "2"]}

How to assign the value to *user_id* in paragraph object before calling
save method

Console output:

Started POST "/documents" for 127.0.0.1 at 2013-03-15 19:17:12 +0530
  Processing by DocumentsController#create as HTML
  Parameters: {"utf8"=>"✓",
"authenticity_token"=>"fvjouziWyDPCsTIJQvguXG1vvAIGy8ej5hR+69TTeIQ=",
"document"=>{"name"=>"sample", 
"sections_attributes"=>{"0"=>{"name"=>"one",
"content_ids"=>["1", "2"]}}}, "commit"=>"submit"}
  Content Load (0.0ms)  SELECT `contents`.* FROM `contents` WHERE
`contents`.`id` IN (1, 2)
  SQL (0.1ms)  BEGIN
  SQL (0.0ms)  COMMIT
  SQL (0.0ms)  BEGIN
  SQL (0.3ms)  describe `documents`
  AREL (0.1ms)  INSERT INTO `documents` (`name`, `created_at`,
`updated_at`) VALUES ('sample', '2013-03-15 13:47:12', '2013-03-15
13:47:12')
  SQL (0.3ms)  describe `sections`
  AREL (0.1ms)  INSERT INTO `sections` (`name`, `document_id`,
`created_at`, `updated_at`) VALUES ('one', 2, '2013-03-15 13:47:12',
'2013-03-15 13:47:12')
  Section Load (0.3ms)  SELECT `sections`.* FROM `sections` WHERE
`sections`.`id` = 3 LIMIT 1
  Content Load (0.1ms)  SELECT `contents`.* FROM `contents` WHERE
`contents`.`id` = 1 LIMIT 1
  SQL (72.5ms)  ROLLBACK
  Content Load (0.1ms)  SELECT `contents`.* FROM `contents`
Rendered documents/_form.html.erb (4.8ms)
Rendered documents/new.html.erb within layouts/application (8.7ms)


Started POST "/documents/2" for 127.0.0.1 at 2013-03-15 19:17:48 +0530
  Processing by DocumentsController#update as HTML
  Parameters: {"utf8"=>"✓",
"authenticity_token"=>"fvjouziWyDPCsTIJQvguXG1vvAIGy8ej5hR+69TTeIQ=",
"document"=>{"name"=>"sample", 
"sections_attributes"=>{"0"=>{"name"=>"one",
"content_ids"=>["1", "2"]}}}, "commit"=>"submit", "id"=>"2"}
  Document Load (0.2ms)  SELECT `documents`.* FROM `documents` WHERE
`documents`.`id` = 2 LIMIT 1
Completed 404 Not Found in 10ms

ActiveRecord::RecordNotFound (Couldn't find Document with ID=2):
  app/controllers/documents_controller.rb:30:in `update'

Console Output

Started POST "/documents" for 127.0.0.1 at 2013-03-15 19:17:12 +0530
  Processing by DocumentsController#create as HTML
  Parameters: {"utf8"=>"✓",
"authenticity_token"=>"fvjouziWyDPCsTIJQvguXG1vvAIGy8ej5hR+69TTeIQ=",
"document"=>{"name"=>"sample", 
"sections_attributes"=>{"0"=>{"name"=>"one",
"content_ids"=>["1", "2"]}}}, "commit"=>"submit"}
  Content Load (0.0ms)  SELECT `contents`.* FROM `contents` WHERE
`contents`.`id` IN (1, 2)
  SQL (0.1ms)  BEGIN
  SQL (0.0ms)  COMMIT
  SQL (0.0ms)  BEGIN
  SQL (0.3ms)  describe `documents`
  AREL (0.1ms)  INSERT INTO `documents` (`name`, `created_at`,
`updated_at`) VALUES ('sample', '2013-03-15 13:47:12', '2013-03-15
13:47:12')
  SQL (0.3ms)  describe `sections`
  AREL (0.1ms)  INSERT INTO `sections` (`name`, `document_id`,
`created_at`, `updated_at`) VALUES ('one', 2, '2013-03-15 13:47:12',
'2013-03-15 13:47:12')
  Section Load (0.3ms)  SELECT `sections`.* FROM `sections` WHERE
`sections`.`id` = 3 LIMIT 1
  Content Load (0.1ms)  SELECT `contents`.* FROM `contents` WHERE
`contents`.`id` = 1 LIMIT 1
  SQL (72.5ms)  ROLLBACK
  Content Load (0.1ms)  SELECT `contents`.* FROM `contents`
Rendered documents/_form.html.erb (4.8ms)
Rendered documents/new.html.erb within layouts/application (8.7ms)


Started POST "/documents/2" for 127.0.0.1 at 2013-03-15 19:17:48 +0530
  Processing by DocumentsController#update as HTML
  Parameters: {"utf8"=>"✓",
"authenticity_token"=>"fvjouziWyDPCsTIJQvguXG1vvAIGy8ej5hR+69TTeIQ=",
"document"=>{"name"=>"sample", 
"sections_attributes"=>{"0"=>{"name"=>"one",
"content_ids"=>["1", "2"]}}}, "commit"=>"submit", "id"=>"2"}
  Document Load (0.2ms)  SELECT `documents`.* FROM `documents` WHERE
`documents`.`id` = 2 LIMIT 1
Completed 404 Not Found in 10ms

ActiveRecord::RecordNotFound (Couldn't find Document with ID=2):
  app/controllers/documents_controller.rb:30:in `update'