Notes posted by himn1

This can be useful for conditional validation

http://rubyquicktips.tumblr.com/post/411400798/conditional-validation-using-with-options-to-improve

Custom validator with i18n support

Here is modified EmailValidator from the example above:

class EmailValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    record.errors.add(attribute, options[:message] || :email) unless
      value =~ /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i
  end
end

And locale:

en:
  activerecord:
    errors:
      messages:
        email: "is not an email"

Attachment's name

Files attached in a standard way are shown up as “noname”. You can specify any name by using the :filename key:

attachment :content_type => "application/pdf",
           :filename     => "Othersheet.pdf",
           :body         => File.read("example.pdf")