A little snippet to add to application_helper to handle errors in a rails 3.2 form. (requires HAML 4). This allows you to replace the generated error explanation at the top of your _form.haml partials

explain_errors.rb

# create this in helpers/feedback_helper.rb
# use version 1 for haml (buggy) or version 2 for erb

# version 1 via haml
require 'haml'

module FeedbackHelper
  def self.included(base)
    base.class_eval do
      include Haml::Helpers
      extend Haml::Helpers
    end
  end

  
  def explain_errors( model )
    init_haml_helpers
    if model.present? && model.errors.any?
      capture_haml do
        haml_tag :h4 do
          haml_concat <<-HERE_DOC
            #{pluralize( model.errors.count, "error")} prohibited this
            #{ model.class } from being saved:
          HERE_DOC
        end
        haml_tag :ul do
          model.errors.full_messages.each do |msg|
            haml_tag :li, msg
          end
        end
      end
    end
  end
end


# version 2 less buggy as its erb
module FeedbackHelper

  # ERB ONLY
  def explain_errors(model)
    if model.present? && model.errors.any?
      html = ""
      html << content_tag(:h4) do
        <<-HERE_DOC
          #{pluralize( model.errors.count, "error")} prohibited this
          #{ model.class } from being saved:
        HERE_DOC
      end
      html << content_tag(:ul) do
        model.errors.full_messages.each {|msg|
          concat(content_tag(:li, msg, class: 'text-error'))
        }
      end
      html.html_safe
    end
  end

end


# leverage this in your haml _form.haml partial with 
= simple_form_for @object do |f|
  = explain_errors @object
  ...

I've tested this with DataMapper and ActiveRecord. It requires the errors method on a model so in data mapper it will require dm-validations.

Blows up with haml 4! Damn you!

fixed for haml 4

ugh. still broken. lol

the erb one works. the other one sometimes needs init_haml_helpers