#211 Validations in Rails 3

Apr 26, 2010 | 9 minutes | Active Record, Views, Forms, Rails 3.0

Rails 3 offers several new additions to validations. Here learn how to make a custom error_messages partial, reflect on validations, and clean up complex validations in a model.

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          bash
        
gem install rails --pre
gem cleanup
rails store
cd store
rails g scaffold user name:string email:string
rake db:migrate

          users/_form.html.erb
        
<%= form_for(@user) do |f| %>
  <%= render "shared/error_messages", :target => @user %>
  
  <div class="field">
    <%= f.label :name %><%= mark_required(@user, :name) %><br />
    <%= f.text_field :name %>
  </div>
  <div class="field">
    <%= f.label :email %><%= mark_required(@user, :email) %><br />
    <%= f.text_field :email %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

          shared/_error_messages.html.erb
        
<% if target.errors.any? %>
<div id="errorExplanation">
  <h2><%= pluralize(target.errors.count, "error") %> prohibited this record from being saved:</h2>
  <ul>
  <% target.errors.full_messages.each do |msg| %>
    <li><%= msg %></li>
  <% end %>
  </ul>
</div>
<% end %>

          application_helper.rb
        
def mark_required(object, attribute)
  "*" if object.class.validators_on(attribute).map(&:class).include? ActiveModel::Validations::PresenceValidator
end

          models/user.rb
        
validates :email, :presence => true, :uniqueness => true, :email_format => true

          lib/email_format_validator.rb
        
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