Rails field_error_proc to add an error class to invalid input fields

field_error_proc.rb

#Overrides the default way how rails marks form fields with errors.
#In this version, it only adds the class 'error' to label and element

ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
  if html_tag =~ /<(input|label|textarea|select)/
    html_field = Nokogiri::HTML::DocumentFragment.parse(html_tag)
    html_field.children.add_class 'error'
    html_field.to_s
  else
    html_tag
  end
end

L8: add .html_safe for newer rails versions

thanks!

@thedanielhanke is there any other way? Rubocop is complaining...

@mrshortt please provide some more details/infos