Gemfile

@@ -16,4 +16,4 @@ end
 
 # To use debugger (ruby-debug for Ruby 1.8.7+, ruby-debug19 for Ruby 1.9.2+)
 # gem 'ruby-debug'
-# gem 'ruby-debug19'
+# gem 'ruby-debug19'

Rakefile

@@ -39,4 +39,4 @@ begin
   Jeweler::GemcutterTasks.new
 rescue LoadError
   puts "Jeweler (or a dependency) not available. Install it with: gem install jeweler"
-end
+end

lib/cocoon.rb

@@ -10,7 +10,11 @@ module Cocoon
     # configure our plugin on boot
     initializer "cocoon.initialize" do |app|
       ActionView::Base.send :include, Cocoon::ViewHelpers
+
+      if Object.const_defined?("Formtastic") and Formtastic.const_defined?("Inputs")
+        require 'cocoon/formtastic/cocoon_input'
+      end
     end
 
   end
-end
+end

lib/cocoon/formtastic/cocoon_input.rb

@@ -0,0 +1,24 @@
+require 'formtastic'
+
+class CocoonInput
+  include ::Formtastic::Inputs::Base
+
+  def to_html
+    output = []
+
+    output << label_html
+
+    output << builder.semantic_fields_for(method) do |fields|
+      if fields.object
+        template.render :partial => "#{method.to_s.singularize}_fields", :locals => { :f => fields }
+      end
+    end
+
+    output << template.content_tag(:div, :class => 'links') do
+      template.link_to_add_association template.t('.add'), builder, method
+    end
+
+    template.content_tag(:li, output.join('').html_safe, :class => 'input cocoon')
+  end
+end
+