gistfile1.rb

      #The point of this method is to try executing a change on CustomField Kind, i.e. changing from string to text.
      #since not all custom fields are interchangeable like this (boolean to integer for example)  this validation
      #executes he query that updates it, forces a rollback by raising an exception, do nothing if the exception was triggered
      #by us(the query ran successfully) and then rescue every other exception and assume it's because of incompoatible types
      
      def validate_value_kind_change
        if should_migrate_values?
          begin
            begin
              self.class.transaction do
                migrate_values(custom_field_values.id_equals(custom_field_values.first.id))
                #doesn't trigger a rollback since we rescue this within the parent transaction, this isn't a "true" subtransaction
                raise RollbackTransaction.new
              end
            rescue RollbackTransaction => e
            end
          rescue Exception => e
            errors.add(:kind, "sorry you can't change from #{kind_was} to #{kind} because the 2 types are not related. Can you convert the data to the other?")
          end
        end
      end
      
      
      def validate_value_kind_change
        if should_migrate_values?
          begin
            #mark this as a true sub transaction
            self.class.transaction(:requires_new => true) do
              migrate_values(custom_field_values.id_equals(custom_field_values.first.id))
              #this is a special active record exception that doesn't bubble up past the transaction so we dont' need to rescue it
              raise  ActiveRecord::Rollback.new
            end
          rescue Exception => e
            errors.add(:kind, "sorry you can't change from #{kind_was} to #{kind} because the 2 types are not related. Can you convert the data to the other?")
          end
        end
      end