Partial and model errors

I have the following two models Ads and Listings.

class Listing < ActiveRecord::Base
belongs_to :ads
end

class Ad < ActiveRecord::Base
has_many :listings
end

In my view to create a new ad, I used a listing partial, because I would
like to use that listing partial in other parts of my project. So the
view looks like:

<%= error_messages_for ‘ad’ %>

Title Ad
<%= text_field 'ad', 'title' %>

Text
<%= text_area 'ad', 'text' %>

<%= render (:partial => “listing/listing”, :object => @listing) %>

The view code of the listing partial is:

Startdatum

<%= select_day (Time.now.day, :prefix => “listing”) %>
<%= select_month (Time.now.month, :prefix => “listing”) %>
<%= select_year (Time.now.year, :prefix => “listing”, :start_year =>
Time.now.year,
:end_year => Time.now.year+1) %>

Aantal weken <%= select (:listing, :number_weeks, [['1 Week', 1], ['2 Weken', 2], ['3 Weken', 3], ['4 Weken', 4], ['5 Weken', 5], ['6 Weken', 6], ['7 Weken', 7], ['8 Weken', 8], ['9 Weken', 9], ['10 Weken', 10]]) %>

Adding a valid ad, with a correct listing works fine. The problem is
when I try to add an ad with an invalid start date. It only save the
data of the ad to the database and not that of the listing. I guessed it
would raise an error and not add any data to the database. In my listing
model I have added validation to validate the correctness of the date,
like so:

def validate
if Date::valid_civil?(year.to_i, month.to_i, day.to_i) == nil
errors.add(:year, day.to_s + “-” + month.to_s + “-” + year.to_s + “is
geen geldige datum.”)
else
self.start_date = year.to_s + “-” + month.to_s + “-” + day.to_s
end
end

The validation works perfect if I only test the listing model without
the integration in the ad model.

In my ad controller I create the ad like:

def create
@ad = Ad.new(params[:ad])
@listing = Listing.new(params[:listing])
@listing.listing_type = “ads”

if @ad.save
  @ad.listings << @listing
  flash[:notice] = 'Ad was successfully created.'
  redirect_to :action => 'list'
else
  render :action => 'new'
end

end

When I save my ad, how can I get Rails to also check for the correctness
of the start date and raise an error if it is not valid? Hope somebody
can give some pointers.

Kind regards,

Nick

I added <%= error_messages_for ‘listing’ %> to my view, so it should
also display listing errors generated by the Listing model. But I’m
missing something, because errors generated by the listing are not
displayed. All suggestions are welcome.

Kind regards,

Nick