File Uploads

To handle a file upload, first you must add a file upload control to your view. The following is HAML for adding a file upload control.

  = form_for(@make, :action => url(:make, @make)) do
    %p
      = text_area :description, :label => "Description"
      = file_field :attachment, :label => "File"
      = submit "Update"

The line we are interested in is:

      = file_field :attachment, :label => "File"

It is important to note, just by adding a file_field to the form, Merb automatically adds the multipart attributes to the form.

Now we have to handle the uploaded file in the controller. When the file is uploaded, your controller gets a hash with the following properties

1. filename, String
2. content_type, String
3. size, Integer
4. tempfile, File

class Attachment
  include DataMapper::Resource
 
  property :id, Serial
  property :filename, String
  property :content_type, String
  property :size, Integer
  property :attachable_id, Integer
  property :attachable_type, String
 
  def url
    "/uploads/#{self.id}/#{self.filename}"
  end
end

require 'ftools'
 
module Attachable
  include FileUtils
 
  def attachments
    @attachments = Attachment.all(:attachable_type => self.class, :attachable_id => self.id)
  end
  def attachment
    @attachment
  end
  def attachment=(value)
    @attachment = value
    unless value.empty?
      attachment = Attachment.create( :attachable_type => self.class,
                                      :attachable_id => self.id,
                                      :filename => @attachment[:filename],
                                      :content_type => @attachment[:content_type],
                                      :size => @attachment[:size]
      )
 
      File.makedirs("public/uploads/#{attachment.id}")
      mv(@attachment[:tempfile].path, "public/uploads/#{attachment.id}/#{attachment.filename}")
 
      # or partition the path if you are expecting a LOT of attachments
      # path = File.join('public', 'uploads', partitioned_path(attachment.id))
      # File.makedirs(path)
      # mv(@attachment[:tempfile].path, File.join(path, attachment.filename))
    end
  end
 
  protected
 
  # Partition the path according to the id
  def partitioned_path(id)
    *("%06d" % id).scan(/.../)
  end
end

You can now attach files to any model by including the Attachable module in your model, and adding the file_field to your edit view.