Twitter Bootstrap FormBuilder

bootstrap_form_builder.rb

# FormBuilder for Ruby on Rails which produces HTML code compatible with Twitter Bootstrap
# horizontal forms styles (see here: http://twitter.github.com/bootstrap/base-css.html#forms)
#
# Features:
#   * displays validation errors in-line
#   * has custom option - label-text - to override default label text for an input
#
# Requirements:
#   By default, Rails will wrap a field with validation error in an ugly div tag that breaks
#   the layout. To override this behaviour, add
#      config.action_view.field_error_proc = Proc.new do |html_tag, instance|
#        "#{html_tag}".html_safe
#      end
#   to config/application.rb
#
# Sample usage:
# <%= form_for @pet, builder: BootstrapFormBuilder, html: { class: "well form-horizontal" } do |f| %>
#   <%= f.text_field :name %>		
#   <%= f.number_field :age, in: 0..50 %>
#   <%= f.collection_select :kind, Pet::KINDS, :to_s, :to_s,
#         include_blank: true, label_text: "My pet is a" %>
#   <%= f.check_box :bites %>
#   <%= f.date_select :birthday, label_text: "Date of birth" %>
#   <%= f.file_field :image %>
#   <div class="form-actions">
#     <%= f.submit "Add pet", class: "btn btn-primary" %>
#   </div>
# <% end %>

class BootstrapFormBuilder < ActionView::Helpers::FormBuilder
  delegate :content_tag, to: :@template
  
  %w[text_field number_field collection_select check_box date_select file_field].each do |method_name|
    define_method(method_name) do |name, *args|          
      content_tag :div, class: "control-group #{"error" if object.errors[name].any?}" do
        label_field(name, *args) + field_div(method_name, name, *args)
      end
    end
  end

  private
  def errors_span(name)
    content_tag :span, class: "help-inline" do
      object.errors[name].first if object.errors[name].any?
    end
  end
  
  def field_div(field, name, *args)
    content_tag :div, class: "controls" do
      self.class.superclass.instance_method(field).bind(self).call(name, *args) + errors_span(name)
    end
  end
  
  def label_field(name, *args)
    options = args.extract_options!
    label(name, options[:label_text], class: "control-label")
  end
end