attachmerb_fu is a port of Rick Olson's famous attachment_fu Rails plugin to merb. It tries to be as orm-agnostic as merb while having the same functionalities as the original plugin.

This plugin is still in a very alpha state and was only tested with datamapper orm, mini_magick image processor and filesystem storage. It may or may not work for your application

Note: attachmerb_fu requires Merb >= 0.5

attachmerb_fu functionality

attachmerb_fu facilitates file uploads in Merb. There are a few storage options for the actual file data, but the plugin always at a minimum stores metadata for each file in the database.

There are three storage options for files uploaded through attachmerb_fu:

File system
Database file (currently not tested)
Amazon S3 (currently not tested)

Each method of storage many options associated with it that will be covered in the following section. Something to note, however, is that the Amazon S3 storage requires you to modify config/amazon_s3.yml and the Database file storage requires an extra table.

attachmerb_fu models

For all three of these storage options a table of metadata is required. This table will contain information about the file (hence the 'meta') and its location. This table has no restrictions on naming, unlike the extra table required for database storage, which must have a table name of db_files (and by convention a model of DbFile).

In the model there are two methods made available by this plugins: has_attachment and validates_as_attachment.

has_attachment(options = {})

This method accepts the options in a hash:
  :content_type     # Allowed content types.
                    # Allows all by default.  Use :image to allow all standard image types.
  :min_size         # Minimum size allowed.
                    # 1 byte is the default.
  :max_size         # Maximum size allowed.
                    # 1.megabyte is the default.
  :size             # Range of sizes allowed.
                    # (1..1.megabyte) is the default.  This overrides the :min_size and :max_size options.
  :resize_to        # Used by RMagick to resize images.
                    # Pass either an array of width/height, or a geometry string.
  :thumbnails       # Specifies a set of thumbnails to generate.
                    # This accepts a hash of filename suffixes and RMagick resizing options.
                    # This option need only be included if you want thumbnailing.
  :thumbnail_class  # Set which model class to use for thumbnails.
                    # This current attachment class is used by default.
  :path_prefix      # path to store the uploaded files.
                    # Uses public/#{table_name} by default for the filesystem, and just #{table_name} for the S3 backend.  
                    # Setting this sets the :storage to :file_system.
  :storage          # Specifies the storage system to use..
                    # Defaults to :db_file.  Options are :file_system, :db_file, and :s3.
  :processor        # Sets the image processor to use for resizing of the attached image.
                    # Options include ImageScience, Rmagick, and MiniMagick.  Default is whatever is installed.

  has_attachment :max_size => 1.kilobyte
  has_attachment :size => 1.megabyte..2.megabytes
  has_attachment :content_type => 'application/pdf'
  has_attachment :content_type => ['application/pdf', 'application/msword', 'text/plain']
  has_attachment :content_type => :image, :resize_to => [50,50]
  has_attachment :content_type => ['application/pdf', :image], :resize_to => 'x50'
  has_attachment :thumbnails => { :thumb => [50, 50], :geometry => 'x50' }
  has_attachment :storage => :file_system, :path_prefix => 'public/files'
  has_attachment :storage => :file_system, :path_prefix => 'public/files', 
                 :content_type => :image, :resize_to => [50,50]
  has_attachment :storage => :file_system, :path_prefix => 'public/files',
                 :thumbnails => { :thumb => [50, 50], :geometry => 'x50' }
  has_attachment :storage => :s3


This method prevents files outside of the valid range (:min_size to :max_size, or the :size range) from being saved.  It does not however, halt the upload of such files.  They will be uploaded into memory regardless of size before validation.


attachmerb_fu migrations

Fields for attachmerb_fu metadata tables…

in general:
  size,         :integer  # file size in bytes
  content_type, :string   # mime type, ex: application/mp3
  filename,     :string   # sanitized filename
that reference images:
  height,       :integer  # in pixels
  width,        :integer  # in pixels
that reference images that will be thumbnailed:
  parent_id,    :integer  # id of parent image (on the same table, a self-referencing foreign-key).
                          # Only populated if the current object is a thumbnail.
  thumbnail,    :string   # the 'type' of thumbnail this attachment record describes.  
                          # Only populated if the current object is a thumbnail.
                          # Usage:
                          # [ In Model 'Avatar' ]
                          #   has_attachment :content_type => :image, 
                          #                  :storage => :file_system, 
                          #                  :max_size => 500.kilobytes,
                          #                  :resize_to => '320x200>',
                          #                  :thumbnails => { :small => '10x10>',
                          #                                   :thumb => '100x100>' }
                          # [ Elsewhere ]
                          # @user.avatar.thumbnails.first.thumbnail #=> 'small'
that reference files stored in the database (:db_file):
  db_file_id,   :integer  # id of the file in the database (foreign key)

Field for attachmerb_fu db_files table:

data, :binary # binary file data, for use in database file storage

attachmerb_fu views

There are two main views tasks that will be directly affected by attachmerb_fu: upload forms and displaying uploaded images.

There are two parts of the upload form that differ from typical usage.

1. Include ':multipart => true' in the html options of the form_for tag.
    <% form_for(:attachment_metadata, :url => { :action => "create" }, :html => { :multipart => true }) do |form| %>

2. Use the file_field helper with :uploaded_data as the field name.
    <%= form.file_field :uploaded_data %>

Displaying uploaded images is made easy by the public_filename method of the ActiveRecord attachment objects using file system and s3 storage.

public_filename(thumbnail = nil)

Returns the public path to the file.  If a thumbnail prefix is specified it will return the public file path to the corresponding thumbnail.
  attachment_obj.public_filename          #=> /attachments/2/file.jpg
  attachment_obj.public_filename(:thumb)  #=> /attachments/2/file_thumb.jpg
  attachment_obj.public_filename(:small)  #=> /attachments/2/file_small.jpg

When serving files from database storage, doing more than simply downloading the file is beyond the scope of this document.

attachmerb_fu controllers

There are two considerations to take into account when using attachmerb_fu in controllers.

The first is when the files have no publicly accessible path and need to be downloaded through an action.


def readme
  send_file '/path/to/readme.txt', :type => 'plain/text', :disposition => 'inline'

See the possible values for send_file for reference.

The second is when saving the file when submitted from a form. Example in view:

<%= form.file_field :attachable, :uploaded_data %>

Example in controller:

def create
  @attachable_file =[:attachable])
    flash[:notice] = 'Attachment was successfully created.'
    redirect_to attachable_url(@attachable_file)     
    render :action => :new