Rails 3 Validations on Field from Related Model

I have a User class that has a UserProfile class. The email is stored in the User table because they need to login with it, however, from my user_profiles#edit method, I'd like to be able to update this email address.

How can I place validations on the email field?

My class looks something like this (obviously not right, but you get the idea):

class UserProfile < ActiveRecord::Base
  belongs_to :user

  validates :first_name, :presence => true
  validates :last_name, :presence => true
  validates :email, :presence => true, :uniqueness => true, :email_fo开发者_C百科rmat => true  

  def email=(email)
    self.user.email = email
    self.user.save
  end
end

My form parameters will look something like:

{
   "user_profile" => { "first_name" => "John", "email" => "qwerty", ....
}

The EmailValidator is just taken from Railscasts:

class EmailFormatValidator < ActiveModel::EachValidator  
  def validate_each(object, attribute, value)  
    unless value =~ /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i  
      object.errors[attribute] << (options[:message] || "is not formatted properly")  
    end  
  end  
end  

You can put your validation in the user model. When you call save on the user model, then those validations are checked.

And you need to add the following to the association:

belongs_to :user, :validate => true, :autosave => true

And remove the save call from the email= method, because now the user is saved automatically.