Parent model running validations on all existing children

In my application, a Language has many Phrases. Here is my code:

#language model
has_many :phrases
accepts_nested_attributes_for :phrases

#phrase model
validates_presence_of :value
belongs_to :language

#languages controller
def edit
   @language = Language.find(params[:id])
   # Let's say we only want to update some of the phrases (e.g. by
category, date, etc)
   @phrases = @language.phrases.all(:limit => 3)
end

def update
   @language = Language.find(params[:id])
   if @language.update_attributes(params[:language])
     flash[:notice] = "Successfully updated language."
     redirect_to edit_language_path(@language)
   else
     render :action => 'edit'
   end
end

# project edit view
<% form_for @language do |f| %>
<%= f.error_messages %>
<p>
   <%= f.label :name %><br />
   <%= f.text_field :name %>
</p>
<% f.fields_for :phrases, @phrases do |phrases_form| %>
   <p>
     <%= phrases_form.label :value %>
     <%= phrases_form.text_field :value %>
   </p>
<% end %>
<p><%= f.submit %></p>
<% end %>

When I submit the form, if at least one of the phrases being saved is
an existing record, every single phrase corresponding to @language
will be validated, instead of running validations only in the three
phrases being updated. That problem isn't present when all of the
phrases being saved are new records.

I was expecting Rails to only validate the phrase that is being updated,
here you can see it's validating all of the existing phrases:

$ script/console
Loading development environment (Rails 2.3.5)

lang = Language.first

=> #<Language id: 1, name: "Italiano">

lang.phrases

=> [#<Phrase id: 7, value: "Buona notte", language_id: 1>,
#<Phrase id: 10, value: "Ciao", language_id: 1>,
#<Phrase id: 11, value: "Prego", language_id: 1>]

lang.phrases_attributes = [{:id => "7", :value => "Buon giorno"}]

=> [{:value=>"Buon giorno", :id=>"7"}]

lang.save

Validating: Buon giorno

Validating: Ciao

Validating: Prego

=> true

My models, again, now with the added "before_validation" callback:

class Language < ActiveRecord::Base
  has_many :phrases
  accepts_nested_attributes_for :phrases
end

class Phrase < ActiveRecord::Base
  validates_presence_of :value
  belongs_to :language
  def before_validation
    logger.debug "\nValidating: #{self.value}\n"
  end
end

Validating all phrases is a real problem in my app, as I have tens of
thousands; Is there a way to avoid this? Is this normal behavior for
Rails?

Ruben Ascencio wrote: