Adding new fields to Spree Variant's additional_fields

yoursite_extension.rb

# Samples for formatting additional Product fields in Spree Admin 
# SelectField: adds a select box with values 1..20
# WideField:   adds a standard text box, but with a specified size
# HugeField:   adds a text area with a specified number of columns
# OptionField: adds an option field
# CheckField: adds a checkbox field.

Variant.additional_fields += [
        { :name => 'SelectField',
          :only => [:product],
          :use  => 'select',
          :value => Proc.new{ (1..20).collect{|i| [i,i]} }
        },
        { :name => 'WideField',
          :only => [:product],
          :options => { :size => '180'}
        },
        { :name => 'HugeField',
          :only => [:product],
          :use  => 'text_area',
          :options => { :cols => '100'}
        },
        { :name => 'OptionField', 
          :only => [:product], 
          :use => 'select', 
          :value => Proc.new {OptionType.all.collect {|o| [ o.name, o.name ] }}
        },
        { :name => 'Featured', 
          :only => [:product],  
          :use => 'check_box', 
          :checked_value => "1", 
          :unchecked_value => "0"
        }
]

# These the above lines in your extension activate method.
    Product.class_eval do 
      named_scope :featured, { :conditions => "products.featured = '1'" }
    end