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} %>
<% 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:

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’