smart_label_form_builder.rb

# 
#  smart_label_form_builder.rb
#
#  original code from:
#   http://openmonkey.com/articles/2010/03/rails-labels-with-blocks
#
#  --
#  adding HAML compatibility (fabrice AT sofa-design DOT net)
#
class SmartLabelFormBuilder < ActionView::Helpers::FormBuilder
  include Haml::Helpers if defined? Haml       # for compatibility
  
  def label(method, content_or_options_with_block = nil, options = {}, &block)
    if !block_given?
      # No block, use the standard label helper.
      super(method, content_or_options_with_block, options)
    else
      # We've got a block. This is where we want to do our business.
      options = content_or_options_with_block.is_a?(Hash) ? content_or_options_with_block.stringify_keys : {}

      if errors_on?(method)
        (options['class'] = options['class'].to_s + ' error').strip!
      end
      
      if block_is_haml?(block)
        init_haml_helpers
        capture_haml(options, block) do |options, block|
          haml_tag(:label, options) do
            haml_concat method.to_s.humanize
            haml_concat capture_haml(&block)
          end
        end
      else
        @template.content_tag(:label, options, &block)
      end
    end
  end

  private

  def errors_on?(method)
    @object.respond_to?(:errors) && @object.errors.respond_to?(:on) && @object.errors.on(method.to_sym)
  end
end

ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
  if instance.error_message.kind_of?(Array)
    %(#{html_tag}<div class="error_description">
      #{instance.error_message * ', '}</div>)
  else
    %(#{html_tag}<div class="error_description">
      #{instance.error_message}</div>)
  end
end