ruby on rails legacy database - primary id retrieved form another table

In my rails app, i have a submission form.

I am using a legacy database where the sub开发者_JAVA百科mission id value is retrieved from a sequence table This sequence value is used as the primary key for my submission

So in my form, i want to pass the sequence value as primary but it's not working

new.html.erb:

<% form_for @submission, :html => { :multipart => true } do |f| %>

<%= f.hidden_field :SUB_OID, :value => $temporary_id %>

<% end %>

submission.rb:

class SubmissionsController < ApplicationController
#retrieve id for new submission
result = ActiveRecord::Base.connection.execute('SELECT SEQ_TEMP_ID FROM ref_sequences')
inc_result = (result.fetch_row.first)


#increment temporary id by 1
$temporary_id = (inc_result.to_i) + 1

def create
@submission = Submission.new(params[:submission])
###@submission.SUB_OID= $temporary_id ###

  if @submission.save

  #after temp submission is saved, update id in ref_sequences table#
  ActiveRecord::Base.connection.execute("UPDATE ref_sequences SET SEQ_TEMP_ID = SEQ_TEMP_ID + 1")

  flash[:notice] = 'Submission was successfully created'
      redirect_to show_submission_path(@submission.SUB_OID)

  else
  render :action => 'new'
  end

end

end

I noticed that the following line does not work:

<%= f.hidden_field :SUB_OID, :value => $temporary_id %>

However, to pass the sequence value as submission id, i have to put the following line in the def create function:

@submission.SUB_OID= $temporary_id

The thing now is i want to know if i can pass the primary id of the submission in the new.html.erb page itself, instaed of declaring it in the def create function.

Many thanks for looking into this..

cheers

---

Better to leave the ID out of your forms and set it on save:

class Submission < ActiveRecord::Base

  before_create :fetch_id
  after_create  :update_sequence_table

private

  def fetch_id
    self[:id] = connection.execute('SELECT SEQ_TEMP_ID FROM ref_sequences')
  end

  def update_sequence_table
    connection.execute("UPDATE ref_sequences SET SEQ_TEMP_ID = SEQ_TEMP_ID + 1")
  end

end