Adding css classes to form

lib/simple_form/action_view_extensions/form_helper.rb

@@ -12,10 +12,17 @@ module SimpleForm
     module FormHelper
       [:form_for, :fields_for, :remote_form_for].each do |helper|
         class_eval <<-METHOD, __FILE__, __LINE__
-          def simple_#{helper}(*args, &block)
+          def simple_#{helper}(record_or_name_or_array, *args, &block)
             options = args.extract_options!
             options[:builder] = SimpleForm::FormBuilder
-            #{helper}(*(args << options), &block)
+            css_class = case record_or_name_or_array
+              when String, Symbol then record_or_name_or_array.to_s
+              when Array then dom_class(record_or_name_or_array.last)
+              else dom_class(record_or_name_or_array)
+            end
+            options[:html] ||= {}
+            options[:html][:class] = "simple_form \#{css_class} \#{options[:html][:class]}".strip
+            #{helper}(record_or_name_or_array, *(args << options), &block)
           end
         METHOD
       end

test/action_view_extensions/form_helper_test.rb

@@ -8,6 +8,21 @@ class FormHelperTest < ActionView::TestCase
     end
   end
 
+  test 'simple form should add default class to form' do
+    simple_form_for :user do |f| end
+    assert_select 'form.simple_form'
+  end
+
+  test 'simple form should add object name as css class to form when object is not present' do
+    simple_form_for :user do |f| end
+    assert_select 'form.simple_form.user'
+  end
+
+  test 'simple form should add object class name as css class to form' do
+    simple_form_for @user do |f| end
+    assert_select 'form.simple_form.user'
+  end
+
   test 'pass options to simple form' do
     simple_form_for :user, :url => '/account', :html => { :id => 'my_form' } do |f| end
     assert_select 'form#my_form'