Advanced Form Builder

form.html.haml

= form_for [:admin, @account], url: :admin_settings, class: 'settings' do |f|
  %section.panel.panel_form
    = f.input :store_name
    = f.input :description, type: :textarea
    = f.input :contact_email

  %section.panel
    %p.input.text
      = f.submit t('admin.settings.save'), class: 'action_button success'

form_builder.rb

class FormBuilder < ActionView::Helpers::FormBuilder

  def label(attribute, text = nil, options = {}, &block)
    text = (text || attribute.to_s.humanize.titleize)
    unless object.nil?
      errors = object.errors[attribute.to_sym]
      if errors.present?
        text += " #{errors.is_a?(Array) ? errors.first : errors}"
      end
    end
    super(attribute, text.html_safe, options, &block)
  end

  def wrapper(attribute, kind = :text, &block)
    html_class = 'input ' + kind.to_s
    html_class += ' input_focus' if object.public_send(attribute).present?
    html_class += ' input_error' if object.errors[attribute.to_sym].present?
    @template.content_tag "p", class: html_class, &block
  end

  def input(attribute, args={}, &block)
    kind = args.fetch(:type, :text)
    wrapper attribute, kind do
      (label attribute) +
      (text_field attribute)
    end
  end
end