ActiveResource::Validations module basics updated

railties/guides/source/active_resource_basics.textile

@@ -69,6 +69,56 @@ person = Person.find(1)
 person.destroy
 </ruby>
 
+h3. Validations
+
+Module to support validation and errors with Active Resource objects. The module overrides Base#save to rescue ActiveResource::ResourceInvalid exceptions and parse the errors returned in the web service response. The module also adds an errors collection that mimics the interface of the errors provided by ActiveRecord::Errors.
+
+h4. Validating client side resources by overriding validation methods in base class
+
+<ruby>
+class Person < ActiveResource::Base
+   self.site = "http://api.people.com:3000/"
+
+   protected
+
+   def validate
+     errors.add("last", "has invalid characters") unless last =~ /[a-zA-Z]*/
+   end
+end
+</ruby>
+
+h4. Validating client side resources
+
+Consider a Person resource on the server requiring both a first_name and a last_name with a validates_presence_of :first_name, :last_name declaration in the model:
+
+<ruby>
+person = Person.new(:first_name => "Jim", :last_name => "")
+person.save                   # => false (server returns an HTTP 422 status code and errors)
+person.valid?                 # => false
+person.errors.empty?          # => false
+person.errors.count           # => 1
+person.errors.full_messages   # => ["Last name can't be empty"]
+person.errors[:last_name]  # => ["can't be empty"]
+person.last_name = "Halpert"
+person.save                   # => true (and person is now saved to the remote service)
+</ruby>
+
+h4. Public instance methods
+
+ActiveResource::Validations have three public instance methods
+
+h5. errors()
+
+This will return errors object that holds all information about attribute error messages
+
+h5. save_with_validation(options=nil)
+
+This validates the resource with any local validations written in base class and then it will try to POST if there are no errors.
+
+h5. valid?
+
+Runs all the local validations and will return true if no errors.
+
 h3. Changelog
 
 * July 30, 2011: Initial version by "Vishnu Atrai":http://github.com/vatrai