Rails - Sep 2007 - Making attachment_fu polymorphic

I am working on a small model mixin called attachment_kung to make
attachment_fu polymorphic, so you no longer need a different table and
Model class for every associated attachment (Productimage, Ad_doc,
etc). All you really need is one model and table to handel all your
attachments - in some cases, anyway. I have the code working, but have
run into one small hitch that I can''t seem to ferret out: after the
attachment is saved to the db (I am using mySQL 5) and I want to
display a list of the attachments, the order they are returned in is
strange. I say ''strange'' because I, at least, cannot descern
what they
are ORDERed BY. They seem to come back grouped (an image an its
thumbnails will come back adjecent to one another), but the order of
the groups (or even the elements within the groups) is unpredictable.

Any help would be appriciated, my code is below.

Thanks in advance,
Paul Saieg

---
module Attachment_kung
  #
  # Attachment_kung: Polymorphic Support For Attachment_fu
  # Version 0.1
  # ---------------------------------------------------------------
  # -- Kung, a potent concentration of effort --
  # ---------------------------------------------------------------
  #
  # Originally written by Paul Saieg, 14 September 2007
  # email me with comments at classicist at gmail dot com
  #
  # Licensed under a Creative Commons Attribution-ShareAlike 2.5
License
  # http://creativecommons.org/licenses/by-sa/2.5/
  #
  ################################### DESCRIPTION
###############################################
  ## Attachment_kung supports a polymorphic use of attachment_fu, so
you no longer need a different table
  ## and Model class for every associated attachment (Productimage,
Ad_doc, etc.). Instead it relies
  ## on a single Model class called ''Attachment'' and a table
called
''attachments'' (or whatever you want
  ## to call them). It dynamically creates a class called
#{CallingClass}_attachment and then returns an
  ## instance of that class with its polymorphic attributes
(whateverable_type/id) set to match its parent
  ## object. It is called by an object, not a class, because a
polymorphic attachment
  ## must necessarily belong to a particular Model object. DRY up your
life.
  ################################### USE
#######################################################
  ## To setup Attachment_kung,
  ## 1. Create the Attachment_fu model and table (I used Attachment
and attachments),
  ##    set them up for polymorphism. Add to the table a column called
path_prefix.
  ##    (I used: belongs_to :attachable, :polymorphic => true for the
model and attachable_type and
  ##    attachable_id for the table); and configure the Attachment_fu
model with
  ##        has_attachment :storage => :file_system
  ##        include Attachment_kung
  ##    Make sure Attachment_kung is *last*, or you will not be able
to display your attachments. Also,
  ##    I have not tested Attachment_kung with :storage => :s3
or :storage => :db_system. I *ought* to
  ##    work, but one never knows until one tries. Sadly, at present,
Attachment_kung has the limitation
  ##    that it can only handle *one* storage system at a time. Maybe
in a further iteration it will let
  ##    one use both the file_system and s3 at the same time. Maybe.
  ## 2. Mix in Attachment_kung to whatever Model(s) you want to have
the attachments and configure them as
  ##    you normally would for attachment_fu,except use
has_polymorphic_attachment instead of
  ##    has_attachment and validates_as_polymorphic_attachment instead
of validates_as_attachment.
  ##    Write the configuration params just as you normally would. For
more info on
  ##    setting up attachemnt_fu see Mike Clark''s excellent tutorial:
  ##    http://clarkware.com/cgi/blosxom/2007/02/24
  ## 3. Give your Attachment_kung-ed Model the correct has_many for
polymorphism
  ##    (I used: has_many :attachments, :as => :attachable);
  ## 4. Set the belongs_to and table_name methods to inside
Attachment_kung''s @class_def variable to
  ##    match what you''ve done so far (the default is Attachment and
attachments). Also set
  ##    the attachables hash in Attachment_kung''s intialize to match
the names of your model''s
  ##    polymorphic attrubutes (the defaults are :attachable_id
and :attachable_type). Finally, set the
  ##    ''file_system'' case default in in intialize statement
to
''public/#{table_name}'' as per your previous
  ##    choice (again, the default is ''public/attachments'')
  ## 5. Install the attachment_fu plugin and double check to make sure
things are set up right.
  ##
  ## To use Attachment_kung,
  ## 1. In your controller, get a Model with Attachment_kung mixed in
from the database
  ##    (@p = Product.find(1), we''ll say)
  ## 2. Call the new_attachment method and pass it the params with the
uploaded_data. The line
  ##    should look something like this: @attachment
@p.new_attachment(params[:attachment])
  ## 3. Attachments, before they are saved, have a class name of
#{CallingClass}_attachment
  ##    (ie if a Product calls new_attachment then the returned
object''s class will be Product_attachment).
  ##    Attachments, after they are saved, can be called either with
the Attachment class (or whatever you
  ##    created as your Attachment_fu model) or by the usual
polymorphic means. All of the usual methods
  ##    are available from Attachment_fu (like public_filename etc.)
  ##    For a more on polymorphic Models see Chad Fowler''s Rails
Recipes.
  ################################### FAIR WARNING
##############################################
  ##    The new_attachment method makes use of EVAL. In case you don''t
know, eval runs whatever string
  ##    it gets as ruby code. If you pass eval "rm *" it will ruin
your day. Be very careful about
  ##    how you use it, and NEVER EVER open it to your users. Also,
Attachment_kung has not yet been
  ##    tested for use with Attachment_fu''s database or s3 strorage.
This software comes with no warranty,
  ##    expressed or implied.
 
#############################################################################################

  @@attachment_config = []
  @@validates_as_attachment = nil

  # adds methods to the class that is mixing the module in
  def self.append_features(someClass)
    @@klass = someClass
     def someClass.has_polymorphic_attachment(config)
       @@attachment_config = config
     end

     def someClass.validates_as_polymorphic_attachment
       @@validates_as_attachment = true
     end
     super
  end

  # may only work for macs. If this is giving you trouble on a PC, try
reversing the direction of the ''/''s
  # this over writes the public_filename method in attachment_fu.
  # NOTA BENE: this over writes attachment_fu''s public_filename, if
you over write attachment_fu''s
  # full_filename, you may also have to over write Attachment_kung''s
public_filename.
  def public_filename(thumbnail = nil)
     if path_prefix != ""
       path_prefix.gsub!(''public'','''') if
path_prefix.include?
(''public'')
       path_prefix + ''/'' + ("%08d" %
main_attachment_id).scan(/..../).map{|e|e.to_s + ''/''}.to_s +
filename
     else
       begin
         Technoweenie::AttachmentFu::Backends::S3Backend::s3_url
         rescue NoMethodError
         raise ''Attachment has a bad path, please delete it and upload
it again''
       end
     end
  end

  # gets the attachment''s id, or its parent''s id if it has one
  def main_attachment_id
    ((respond_to?(:parent_id) && parent_id) || id).to_i
  end

  # creates the dynamic attachment class and returns an object of that
type with its polymorphic
  # attributes set to reflect the caller
  def new_attachment(params)
    # name of calling class
    class_name = self.class.to_s

    # id of calling object
    parent = self.object_id

    # options from has_polymorphic_attachment
    options = {}
    options.merge!(@@attachment_config)

    # whether validate_as_polymorphic_attachment is set in caller
(default is nil)
    valid = @@validates_as_attachment

    @class_def = %{
      class Object::#{class_name}_attachment < ActiveRecord::Base
        # set polymorphic column names (whateverable_id/type)
        belongs_to :attachable, :polymorphic => true

        # set table into which model will be saved
        self.table_name = "attachments"

        # Initialize polymorphic attributes (attachable_id/type) with
data from parent obj;
        # also initialize value of path_prefix column for
public_filename to use.
        # NOTE: if you are working with different polymorphic column
names be sure to update them
        # from my :attachable_id and :attachable_type to whatever you
are using. Also, be sure to
        # update the default value for ''path'' in the
file_system case
from ''attachements''
        # to whatever your table name is.

        def initialize(attributes={})
          @p = ObjectSpace._id2ref(#{parent})
          path = if "#{@@attachment_config[:path_prefix]}".to_s ==
""
                 pth = case "#{@@attachment_config[:storage]}".to_s
                           when "file_system"
                             "public/attachments"
                           when "db_system"
                             ""
                           when "s3"
                             ""
                           else
                             ""
                     end
                 else
                   pth = "#{@@attachment_config[:path_prefix]}".to_s
                 end
          if respond_to?(:path_prefix)
             attachables = {:attachable_id => @p.id, :attachable_type
=> @p.class.to_s, :path_prefix => path}
           else
             attachables = {:attachable_id => @p.id, :attachable_type
=> @p.class.to_s}
           end
          attributes.merge!(attachables)
          super(attributes)
        end

        # Passes the params from the parent model (passed to
has_polymorphic_attachment) to
        # the attachment_fu''s has_attachment. Also runs
attachment_fu''s validations,
        # if validates_as_polymorphic_attachment was called by the
calling Model
        def self.attach(opts, valid)
          has_attachment opts
          validates_as_attachment if valid
        end

        ##END Class
      end
      }

      eval @class_def

      eval("#{class_name}_attachment").attach(options, valid)
      attachment = eval("#{class_name}_attachment").new(params)
      return attachment
  end


## END MODULE
end


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Here this is version 0.2 of attachment_kung. It has a few bugs worked
out, is a bit faster, but the order of the ''attachments'' table
is
still unpredictable. Any help would be appreciated.

Thanks in advance,
Paul Saieg
>   #Attachment_kung: Polymorphic Support For Attachment_fu
>   # Version 0.2
>   # Originally written by Paul Saieg, 14 September 2007
>   # email me with comments at classicist at gmail dot com
>   #
>   # Licensed under a Creative Commons Attribution-ShareAlike 2.5 License
>   # http://creativecommons.org/licenses/by-sa/2.5/
module Attachment_kung
  @@attachment_config = []
  @@validates_as_attachment = nil

  # adds methods to the class that is mixing the module in
  def self.append_features(someClass)
    @@klass = someClass
     def someClass.has_polymorphic_attachment(config)
       @@attachment_config = config
     end

     def someClass.validates_as_polymorphic_attachment
       @@validates_as_attachment = true
     end
     super
  end


  # Gets the full path to the filename in this format:
  #
  #   # This assumes a model name like MyModel
  #   # public/#{table_name} is the default filesystem path
  #   RAILS_ROOT/public/my_models/5/blah.jpg
  #
  # The optional thumbnail argument will output the thumbnail''s
filename.
  def full_filename(thumbnail = nil)
    file_system_path = (thumbnail ? thumbnail_class :
self).path_prefix.to_s
    File.join(RAILS_ROOT, file_system_path,
*partitioned_path(thumbnail_name_for(thumbnail)))
  end

  # may only work for macs. If this is giving you trouble on a PC, try
reversing the direction of the ''/''s
  def public_filename(thumbnail = nil)
     if path_prefix != ""
       path_prefix.gsub!(''public'','''') if
path_prefix.include?
(''public'')
       path_prefix + ''/'' + ("%08d" %
main_attachment_id).scan(/..../).map{|e|e.to_s + ''/''}.to_s +
filename
     else
       begin
         Technoweenie::AttachmentFu::Backends::S3Backend::s3_url
         rescue NoMethodError
         raise ''Attachment has a bad path, please delete it and upload
it again''
       end
     end
  end

  # gets the attachment''s id, or its parent''s id if it has one
  def main_attachment_id
    ((respond_to?(:parent_id) && parent_id) || id).to_i
  end

  # creates the dynamic attachment class and returns an object of that
type with its polymorphic
  # attributes set to reflect the caller
  def new_attachment(params)

    # name of calling class
    class_name = self.class.to_s

    # id of calling object
    parent = self.object_id

    # options from has_polymorphic_attachment
    options = {}
    options.merge!(@@attachment_config)

    # whether validate_as_polymorphic_attachment is set in caller
(default is nil)
    valid = @@validates_as_attachment

    @class_def = %{
      class Object::#{class_name}_attachment < ActiveRecord::Base

       belongs_to :attachable, :polymorphic => true
        self.table_name = "attachments"

       # intialize object, only tested with :storage_type
=> :file_system
        def initialize(attributes={})
          @p = nil
          @p = ObjectSpace._id2ref(#{parent})
          path = if "#{@@attachment_config[:path_prefix]}".to_s ==
""
                 "public/attachments"
                 else
                  "#{@@attachment_config[:path_prefix]}".to_s
                 end
          if respond_to?(:path_prefix)
             attachables = {:attachable_id => @p.id, :attachable_type
=> @p.class.to_s, :path_prefix => path}
           else
             attachables = {:attachable_id => @p.id, :attachable_type
=> @p.class.to_s}
           end
           @p = nil
          attributes.merge!(attachables)
          super(attributes)
        end

        def self.attach(opts, valid)
          has_attachment opts
          validates_as_attachment if valid
        end

        ##END Class
      end
      }

      eval @class_def

      eval("#{class_name}_attachment").attach(options, valid)
      attachment = eval("#{class_name}_attachment").new(params)
      return attachment
  end


## END MODULE
end


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I am pleased to announce that attachment_kung has been tested and
works. The ordering problem had nothing to do with the code, but was
the result of using a myISAM table rather than an InnoDB table. An
InnoDB table is crucial for the ordering to work. Below is the
completed code. Enjoy it, and please let me know if anyone runs into
any problems (I haven''t tested every possible use case).

- Paul Saieg

module Attachment_kung
  #
  # Attachment_kung: Polymorphic Support For Attachment_fu
  # Version 0.3
  #
  # Originally written by Paul Saieg, 14 September 2007
  # email me with comments at classicist at gmail dot com
  #
  # Licensed under a Creative Commons Attribution-ShareAlike 2.5
License
  # http://creativecommons.org/licenses/by-sa/2.5/
  #
  ################################### DESCRIPTION
###############################################
  ## Attachment_kung supports a polymorphic use of attachment_fu, so
you no longer need a different table
  ## and Model class for every associated attachment (Productimage,
Ad_doc, etc.). Instead it relies
  ## on a single Model class called ''Attachment'' and a table
called
''attachments'' (or whatever you want
  ## to call them). It dynamically creates a class called
#{CallingClass}_attachment and then returns an
  ## instance of that class with its polymorphic attributes
(whateverable_type/id) set to match its parent
  ## object. It is called by an object, not a class, because a
polymorphic attachment
  ## must necessarily belong to a particular Model object. DRY up your
life.
  ################################### USE
#######################################################
  ## To setup Attachment_kung,
  ## 1. Create the Attachment_fu model and table (I used Attachment
and attachments),
  ##    set them up for polymorphism. If you are using mySQL, make
sure the table is InnoDB
  ##    (myISAM will not work). Add to the table a column called
path_prefix.
  ##    (I used: belongs_to :attachable, :polymorphic => true for the
model and attachable_type and
  ##    attachable_id for the table); and configure the Attachment_fu
model with
  ##        has_attachment :storage => :file_system
  ##        include Attachment_kung
  ##    Make sure Attachment_kung is *last*, or you will not be able
to display your attachments. Also,
  ##    I have not tested Attachment_kung with :storage => :s3
or :storage => :db_system. I *ought* to
  ##    work, but one never knows until one tries. Sadly, at present,
Attachment_kung has the limitation
  ##    that it can only handle *one* storage system at a time. Maybe
in a further iteration it will let
  ##    one use both the file_system and s3 at the same time. Maybe.
  ## 2. Mix in Attachment_kung to whatever Model(s) you want to have
the attachments and configure them as
  ##    you normally would for attachment_fu,except use
has_polymorphic_attachment instead of
  ##    has_attachment and validates_as_polymorphic_attachment instead
of validates_as_attachment.
  ##    Write the configuration params just as you normally would. For
more info on
  ##    setting up attachemnt_fu see Mike Clark''s excellent tutorial:
  ##    http://clarkware.com/cgi/blosxom/2007/02/24
  ## 3. Give your Attachment_kung-ed Model the correct has_many for
polymorphism
  ##    (I used: has_many :attachments, :as => :attachable);
  ## 4. Set the belongs_to and table_name methods to inside
Attachment_kung''s @class_def variable to
  ##    match what you''ve done so far (the default is Attachment and
attachments). Also set
  ##    the attachables hash in Attachment_kung''s intialize to match
the names of your model''s
  ##    polymorphic attrubutes (the defaults are :attachable_id
and :attachable_type). Finally, set the
  ##    ''file_system'' case default in in intialize statement
to
''public/#{table_name}'' as per your previous
  ##    choice (again, the default is ''public/attachments'')
  ## 5. Install the attachment_fu plugin and double check to make sure
things are set up right.
  ##
  ## To use Attachment_kung,
  ## 1. In your controller, get a Model with Attachment_kung mixed in
from the database
  ##    (@p = Product.find(1), we''ll say)
  ## 2. Call the new_attachment method and pass it the params with the
uploaded_data. The line
  ##    should look something like this: @attachment
@p.new_attachment(params[:attachment])
  ## 3. Attachments, before they are saved, have a class name of
#{CallingClass}_attachment
  ##    (ie if a Product calls new_attachment then the returned
object''s class will be Product_attachment).
  ##    Attachments, after they are saved, can be called either with
the Attachment class (or whatever you
  ##    created as your Attachment_fu model) or by the usual
polymorphic means. All of the usual methods
  ##    are available from Attachment_fu (like public_filename etc.)
  ##    For a more on polymorphic Models see Chad Fowler''s Rails
Recipes.
  ################################### FAIR WARNING
##############################################
  ##    The new_attachment method makes use of EVAL. In case you don''t
know, eval runs whatever string
  ##    it gets as ruby code. If you pass eval "rm *" it will ruin
your day. Be very careful about
  ##    how you use it, and NEVER EVER open it to your users. Also,
Attachment_kung has not yet been
  ##    tested for use with Attachment_fu''s database or s3 strorage.
This software comes with no warranty,
  ##    expressed or implied.
 
#############################################################################################

  @@attachment_config = []
  @@validates_as_attachment = nil

  # adds methods to the class that is mixing the module in
  def self.append_features(someClass)
    @@klass = someClass
     def someClass.has_polymorphic_attachment(config)
       @@attachment_config = config
     end

     def someClass.validates_as_polymorphic_attachment
       @@validates_as_attachment = true
     end
     super
  end


  # Gets the full path to the filename in this format:
  #
  #   # This assumes a model name like MyModel
  #   # public/#{table_name} is the default filesystem path
  #   RAILS_ROOT/public/my_models/5/blah.jpg
  #
  # The optional thumbnail argument will output the thumbnail''s
filename.
  def full_filename(thumbnail = nil)
    file_system_path = (thumbnail ? thumbnail_class :
self).path_prefix.to_s
    File.join(RAILS_ROOT, file_system_path,
*partitioned_path(thumbnail_name_for(thumbnail)))
  end

  # May only work for macs. If this is giving you trouble on a PC,
try
  # reversing the direction of the ''/''s
  def public_filename(thumbnail = nil)
     if path_prefix != ""
       path_prefix.gsub!(''public'','''') if
path_prefix.include?
(''public'')
       path_prefix + ''/'' + ("%08d" %
main_attachment_id).scan(/..../).map{|e|e.to_s + ''/''}.to_s +
filename
     else
       begin
         Technoweenie::AttachmentFu::Backends::S3Backend::s3_url
         rescue NoMethodError
         raise ''Attachment has a bad path, please delete it and upload
it again''
       end
     end
  end

  # gets the attachment''s id, or its parent''s id if it has one
  def main_attachment_id
    ((respond_to?(:parent_id) && parent_id) || id).to_i
  end

  # creates the dynamic attachment class and returns an object of that
type with its polymorphic
  # attributes set to reflect the caller
  def new_attachment(params)

    # name of calling class
    class_name = self.class.to_s

    # id of calling object
    parent = self.object_id

    # options from has_polymorphic_attachment
    options = {}
    options.merge!(@@attachment_config)

    # whether validate_as_polymorphic_attachment is set in caller
(default is nil)
    valid = @@validates_as_attachment

    @class_def = %{
      class Object::#{class_name}_attachment < ActiveRecord::Base
        # set polymorphic column names (whateverable_id/type)
        belongs_to :attachable, :polymorphic => true

        # set table into which model will be saved
        self.table_name = "attachments"

        # Initialize polymorphic attributes (attachable_id/type) with
data from parent obj;
        # also initialize value of path_prefix column for
public_filename to use.
        # NOTE: if you are working with different polymorphic column
names be sure to update them
        # from my :attachable_id and :attachable_type to whatever you
are using. Also, be sure to
        # update the default value for ''path'' in the
file_system case
from ''attachements''
        # to whatever your table name is.

        def initialize(attributes={})
          @p = nil
          @p = ObjectSpace._id2ref(#{parent})
          path = if "#{@@attachment_config[:path_prefix]}".to_s ==
""
                 "public/attachments"
                 else
                  "#{@@attachment_config[:path_prefix]}".to_s
                 end
          if respond_to?(:path_prefix)
             attachables = {:attachable_id => @p.id, :attachable_type
=> @p.class.to_s, :path_prefix => path}
           else
             attachables = {:attachable_id => @p.id, :attachable_type
=> @p.class.to_s}
           end
           @p = nil
          attributes.merge!(attachables)
          super(attributes)
        end

        # passes attachment_fu it''s options hash and runs its
validations
        def self.attach(opts, valid)
          has_attachment opts
          validates_as_attachment if valid
        end

        ##END Class
      end
      }

      eval @class_def

      eval("#{class_name}_attachment").attach(options, valid)
      attachment = eval("#{class_name}_attachment").new(params)
      return attachment
  end


## END MODULE
end


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