Implements a meta-language for validating managed objects. Typically used in Validator objects but can be included in managed objects too.

Additional og-related validation macros can be found in lib/og/validation.

The following validation macros are available:

 * validate_value
 * validate_confirmation
 * validate_format
 * validate_length
 * validate_inclusion

Og/Database specific validation methods are added in the file og/validation.rb

Example

class User

   attr_accessor :name, String
   attr_accessor :level, Fixnum

   validate_length :name, :range => 2..6
   validate_unique :name, :msg => :name_allready_exists
   validate_format :name, :format => /[a-z]*/, :msg => 'invalid format', :on => :create
 end

 class CustomUserValidator
   include Validation
   validate_length :name, :range => 2..6, :msg_short => :name_too_short, :msg_long => :name_too_long
 end

 user = @request.fill(User.new)
 user.level = 15

 unless user.valid?
   user.save
 else
   p user.errors[:name]
 end

 unless user.save
   p user.errors.on(:name)
 end

 unless errors = CustomUserValidator.errors(user)
   user.save
 else
   p errors[:name]
 end