application_helper.rb

module ApplicationHelper
  # Format errors for display.
  # Resource may be a model or an handler - just anything including ActiveModel::Validations
  #
  # @param [Object] resource the source of errors
  # @return [String] the error html
  def error_messages_for_handler( resource )
    message = <<-EOS
      <div id="error_explanation">
        <ul>
          %s
        </ul>
      </div>
    EOS

    lines = resource.errors.full_messages.map { |msg| '<li>%s</li>' % msg }.join( "\n" )
    ( message % lines ).html_safe
  end
end