Question

How do you display form field highlighting for fields that fail validation errors in Rails 3.1? I know that scaffolding automatically generates the css and controller code to handle this, but I was wondering if there was a way to generate that manually. I have already implemented the string display of error messages through: @user.errors.full_messages.each…etc, but I can’t get the fields to become highlighted in red. Any ideas?

Thanks.

Answer 1

Assuming you have an error class for fields in your CSS file:

<% if @user.errors[:name] %>
  <%= f.label :name, :class => "error" %>
<% else %>
  <%= f.label :name %>
<% end %>

Is this what you want?

Extra: here’s a section about customizing default ActiveRecord validations CSS.

Edit: (about extra ifs)

# app/helpers/application_helper.rb

def field_class(resource, field_name)
  if resource.errors[field_name]
    return "error".html_safe
  else
    return "".html_safe
  end
end

And then:

# in your view

<%= f.label :name, :class => field_class(@user, :name) %>
<%= f.label :password, :class => field_class(@user, :password) %>
[...]

(I may have make a mistake in there – I’m writing on a phone – but you get the general idea. You can code this in number of ways = infinity, so do it the way you like…)