def has_attached_file name, options = {}
      include InstanceMethods

      write_inheritable_attribute(:attachment_definitions, {}) if attachment_definitions.nil?
      attachment_definitions[name] = {:validations => []}.merge(options)

      after_save :save_attached_files
      before_destroy :destroy_attached_files

      define_paperclip_callbacks :post_process, :"#{name}_post_process"

      define_method name do |*args|
        a = attachment_for(name)
        (args.length > 0) ? a.to_s(args.first) : a
      end

      define_method "#{name}=" do |file|
        attachment_for(name).assign(file)
      end

      define_method "#{name}?" do
        attachment_for(name).file?
      end

      validates_each(name) do |record, attr, value|
        attachment = record.attachment_for(name)
        attachment.send(:flush_errors)
      end
    end
def has_attached_file name, options = {}
      include InstanceMethods

      write_inheritable_attribute(:attachment_definitions, {}) if attachment_definitions.nil?
      attachment_definitions[name] = {:validations => []}.merge(options)

      after_save :save_attached_files
      before_destroy :destroy_attached_files

      define_paperclip_callbacks :post_process, :"#{name}_post_process"

      define_method name do |*args|
        a = attachment_for(name)
        (args.length > 0) ? a.to_s(args.first) : a
      end

      define_method "#{name}=" do |file|
        attachment_for(name).assign(file)
      end

      define_method "#{name}?" do
        attachment_for(name).file?
      end

      validates_each(name) do |record, attr, value|
        attachment = record.attachment_for(name)
        attachment.send(:flush_errors)
      end
    end
+has_attached_file+ gives the class it is called on an attribute that maps to a file. This
 is typically a file stored somewhere on the filesystem and has been uploaded by a user.
 The attribute returns a Paperclip::Attachment object which handles the management of
 that file. The intent is to make the attachment as much like a normal attribute. The
 thumbnails will be created when the new file is assigned, but they will *not* be saved
 until +save+ is called on the record. Likewise, if the attribute is set to +nil+ is
 called on it, the attachment will *not* be deleted until +save+ is called. See the
 Paperclip::Attachment documentation for more specifics. There are a number of options
 you can set to change the behavior of a Paperclip attachment:
 * +url+: The full URL of where the attachment is publically accessible. This can just
   as easily point to a directory served directly through Apache as it can to an action
   that can control permissions. You can specify the full domain and path, but usually
   just an absolute path is sufficient. The leading slash *must* be included manually for
   absolute paths. The default value is
   "/system/:attachment/:id/:style/:filename". See
   Paperclip::Attachment#interpolate for more information on variable interpolaton.
     :url => "/:class/:attachment/:id/:style_:filename"
     :url => "http://some.other.host/stuff/:class/:id_:extension"
 * +default_url+: The URL that will be returned if there is no attachment assigned.
   This field is interpolated just as the url is. The default value is
   "/:attachment/:style/missing.png"
     has_attached_file :avatar, :default_url => "/images/default_:style_avatar.png"
     User.new.avatar_url(:small) # => "/images/default_small_avatar.png"
 * +styles+: A hash of thumbnail styles and their geometries. You can find more about
   geometry strings at the ImageMagick website
   (http://www.imagemagick.org/script/command-line-options.php#resize). Paperclip
   also adds the "#" option (e.g. "50x50#"), which will resize the image to fit maximally
   inside the dimensions and then crop the rest off (weighted at the center). The
   default value is to generate no thumbnails.
 * +default_style+: The thumbnail style that will be used by default URLs.
   Defaults to +original+.
     has_attached_file :avatar, :styles => { :normal => "100x100#" },
                       :default_style => :normal
     user.avatar.url # => "/avatars/23/normal_me.png"
 * +whiny+: Will raise an error if Paperclip cannot post_process an uploaded file due
   to a command line error. This will override the global setting for this attachment.
   Defaults to true. This option used to be called :whiny_thumbanils, but this is
   deprecated.
 * +convert_options+: When creating thumbnails, use this free-form options
   array to pass in various convert command options.  Typical options are "-strip" to
   remove all Exif data from the image (save space for thumbnails and avatars) or
   "-depth 8" to specify the bit depth of the resulting conversion.  See ImageMagick
   convert documentation for more options: (http://www.imagemagick.org/script/convert.php)
   Note that this option takes a hash of options, each of which correspond to the style
   of thumbnail being generated. You can also specify :all as a key, which will apply
   to all of the thumbnails being generated. If you specify options for the :original,
   it would be best if you did not specify destructive options, as the intent of keeping
   the original around is to regenerate all the thumbnails when requirements change.
     has_attached_file :avatar, :styles => { :large => "300x300", :negative => "100x100" }
                                :convert_options => {
                                  :all => "-strip",
                                  :negative => "-negate"
                                }
   NOTE: While not deprecated yet, it is not recommended to specify options this way.
   It is recommended that :convert_options option be included in the hash passed to each
   :styles for compatability with future versions.
   NOTE: Strings supplied to :convert_options are split on space in order to undergo
   shell quoting for safety. If your options require a space, please pre-split them
   and pass an array to :convert_options instead.
 * +storage+: Chooses the storage backend where the files will be stored. The current
   choices are :filesystem and :s3. The default is :filesystem. Make sure you read the
   documentation for Paperclip::Storage::Filesystem and Paperclip::Storage::S3
   for backend-specific options.