Introduce validates_with to encapsulate attribute validations in a class.

[#2630 state:committed]

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

2 files changed, 69 insertions, 0 deletions

diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 68b0251982..2f1e7573d8 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -69,6 +69,7 @@ module ActiveRecord
   autoload :TestCase, 'active_record/test_case'
   autoload :Timestamp, 'active_record/timestamp'
   autoload :Transactions, 'active_record/transactions'
+  autoload :Validator, 'active_record/validator'
   autoload :Validations, 'active_record/validations'
 
   module AttributeMethods
diff --git a/activerecord/lib/active_record/validator.rb b/activerecord/lib/active_record/validator.rb
new file mode 100644
index 0000000000..83a33f4dcd
--- /dev/null
+++ b/activerecord/lib/active_record/validator.rb
@@ -0,0 +1,68 @@
+module ActiveRecord #:nodoc:
+
+  # A simple base class that can be used along with ActiveRecord::Base.validates_with
+  #
+  #   class Person < ActiveRecord::Base
+  #     validates_with MyValidator
+  #   end
+  #
+  #   class MyValidator < ActiveRecord::Validator
+  #     def validate
+  #       if some_complex_logic
+  #         record.errors[:base] = "This record is invalid"
+  #       end
+  #     end
+  #
+  #     private
+  #       def some_complex_logic
+  #         # ...
+  #       end
+  #   end
+  #
+  # Any class that inherits from ActiveRecord::Validator will have access to <tt>record</tt>,
+  # which is an instance of the record being validated, and must implement a method called <tt>validate</tt>.
+  #
+  #   class Person < ActiveRecord::Base
+  #     validates_with MyValidator
+  #   end
+  #
+  #   class MyValidator < ActiveRecord::Validator
+  #     def validate
+  #       record # => The person instance being validated
+  #       options # => Any non-standard options passed to validates_with
+  #     end
+  #   end
+  #
+  # To cause a validation error, you must add to the <tt>record<tt>'s errors directly
+  # from within the validators message
+  #
+  #   class MyValidator < ActiveRecord::Validator
+  #     def validate
+  #       record.errors[:base] << "This is some custom error message"
+  #       record.errors[:first_name] << "This is some complex validation"
+  #       # etc...
+  #     end
+  #   end
+  #
+  # To add behavior to the initialize method, use the following signature:
+  #
+  #   class MyValidator < ActiveRecord::Validator
+  #     def initialize(record, options)
+  #       super
+  #       @my_custom_field = options[:field_name] || :first_name
+  #     end
+  #   end
+  #
+  class Validator
+    attr_reader :record, :options
+
+    def initialize(record, options)
+      @record = record
+      @options = options
+    end
+
+    def validate
+      raise "You must override this method"
+    end
+  end
+end