Validation of other model fields

I've got in my Form not only fileds from my model but also fields from
ither models. How can I validate them like other fields.

Example names od input tag fields

<p><label for="model1_name1">Name1</label>
<%= text_field 'model1', 'name1' , :size => 40 %></p>

<p><label for="model1_name2">Name2</label>
<%= text_field 'model1', 'name2' , :size => 40 %></p>

and from different model:

<p><label for="model2_name3">Name3</label>
<%= text_field 'model2', 'name3' , :size => 40 %></p>

How can I validate presence_of field name3 from model2 model??

The update_attributes method saves as well as updating the attribute.


Stephan Wehner wrote:

Daniello, hopefully the following will help move you forward. It will leave you with an @errors for both models in your view that you can iterate over

When managing validations for multiple models in one action I typically use something like the following:

     @model1 =[:model1])
     @model2 =[:model2])

     respond_to do |format|
       if @ model1.valid? && @ model2.valid?
         #TODO: transaction here would help out
         flash[:notice] = 'Model1 and Model2 were successfully created.'
         format.html { render :partial => "my_partial" }
         flash[:notice] = 'There were errors validating model1, model2'
         #merge_errors (below), merges the errors of 2 models into one errors list
         format.html { @errors = merge_errors(@model1, @model2); render :partial => "/error_messages", :errors => @errors, :status => 500 }

   #merges errors from 2 instances into 1 error object
   def merge_errors(model1, model2)
     if model1.errors.size > 0 && model2.errors.size > 0
       model1.errors.instance_eval { @errors.merge model2.errors.instance_values['errors'] }
     elsif model1.errors.size > 0
     elsif model2.errors.size > 0

General Partner
The nNovation Group inc.



If there is a model association between the two models you can use the
following (copy/pasted from


Validates whether the associated object or objects are all valid
themselves. Works with any kind of association.

  class Book < ActiveRecord::Base
    has_many :pages
    belongs_to :library

    validates_associated :pages, :library

Warning: If, after the above definition, you then wrote:

  class Page < ActiveRecord::Base
    belongs_to :book

    validates_associated :book

...this would specify a circular dependency and cause infinite

NOTE: This validation will not fail if the association hasn't been
assigned. If you want to ensure that the association is both present
and guaranteed to be valid, you also need to use

Configuration options:

    * on Specifies when this validation is active (default is :save,
other options :create, :update)
    * if - Specifies a method, proc or string to call to determine if
the validation should

occur (e.g. :if => :allow_validation, or :if => { |user|
user.signup_step > 2 }). The method, proc or string should return or
evaluate to a true or false value.

Bas van Westing

now how did I miss that ?!

This is clearly a better route to go - for you and me, Daniello.

thanx Bas