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======================================================================================


DelayedPaperclip lets you process your [Paperclip](http://github.com/thoughtbot/paperclip) attachments in a
background task with [DelayedJob](https://github.com/collectiveidea/delayed_job), [Resque](https://github.com/resque/resque) or [Sidekiq](https://github.com/mperham/sidekiq).

Why?
----

The most common use case for Paperclip is to easily attach image files
to ActiveRecord models. Most of the time these image files will have
multiple styles and will need to be resized when they are created. This
is usually a pretty [slow operation](http://www.jstorimer.com/ruby/2010/01/05/speep-up-your-paperclip-tests.html) and should be handled in a
background task.

I’m sure that everyone knows this, this gem just makes it easy to do.

Installation
------------

Install the gem:

````
gem install delayed_paperclip
````

Or even better, add it to your Gemfile.

````
source "https://rubygems.org"
gem 'delayed_paperclip'
````

Dependencies:

-   Paperclip
-   DJ, Resque or Sidekiq

Usage
-----

In your model:

````ruby
class User < ActiveRecord::Base
  has_attached_file :avatar, styles: {
                                       medium: "300x300>",
                                       thumb: "100x100>"
                                     }

  process_in_background :avatar
end
````

Use your Paperclip attachment just like always in controllers and views.

To select between using Resque or Delayed::Job, just install and
configure your choice properly within your application, and
delayed_paperclip will do the rest. It will detect which library is
loaded and make a decision about which sort of job to enqueue at that
time.

### Resque

Make sure that you have [Resque](https://github.com/resque/resque) up and running. The jobs will be
dispatched to the <code>:paperclip</code> queue, so you can correctly
dispatch your worker. Configure resque and your workers exactly as you
would otherwise.

### DJ

Just make sure that you have DJ up and running.

### Sidekiq

Make sure that [Sidekiq](http://github.com/mperham/sidekiq) is running and listening to the
`paperclip` queue, either by adding it to your
`sidekiq.yml` config file under `- queues:` or by
passing the command line argument `-q paperclip` to Sidekiq.

### Displaying images during processing

In the default setup, when you upload an image for the first time and
try to display it before the job has been completed, Paperclip will be
none the wiser and output the url of the image which is yet to be
processed, which will result in a broken image link being displayed on
the page.

To have the missing image url be outputted by paperclip while the image is being processed, all you need to do is add a
`#{attachment_name}_processing` column to the specific model you want
to enable this feature for. This feature gracefully degrades and will not affect models which do not have the column added to them.

````ruby
class AddAvatarProcessingToUser < ActiveRecord::Migration
  def self.up
    add_column :users, :avatar_processing, :boolean
  end

  def self.down
    remove_column :users, :avatar_processing
  end
end

@user = User.new(avatar: File.new(...))
@user.save
@user.avatar.url #=> "/images/original/missing.png"
Delayed::Worker.new.work_off

@user.reload
@user.avatar.url #=> "/system/images/3/original/IMG_2772.JPG?1267562148"
````

#### Custom image for processing

This is useful if you have a difference between missing images and
images currently being processed.

````ruby
class User < ActiveRecord::Base
  has_attached_file :avatar

  process_in_background :avatar, processing_image_url: "/images/original/processing.jpg"
end

@user = User.new(avatar: File.new(...))
@user.save
@user.avatar.url #=> "/images/original/processing.png"
Delayed::Worker.new.work_off

@user.reload
@user.avatar.url #=> "/system/images/3/original/IMG_2772.JPG?1267562148"
````

You can also define a custom logic for `processing_image_url`, for
example to display the original\
picture while specific formats are being processed.

````ruby
class Item < ActiveRecord::Base
  has_attached_file :photo

  process_in_background :photo, processing_image_url: :processing_image_fallback

  def processing_image_fallback
    options = photo.options
    options[:interpolator].interpolate(options[:url], photo, :original)
  end
end
````

#### Have processing? status available, but construct image URLs as if delayed_paperclip wasn’t present

If you define the `#{attachment_name}_processing` column, but set the
`url_with_processing` option to false, this opens up other options (other than modifying the url that paperclip returns) for giving feedback to the user while the image is processing. This is useful for advanced situations, for example when dealing with caching systems.

Note especially the method #processing? which passes through the value
of the boolean created via migration.

````ruby
class User < ActiveRecord::Base
  has_attached_file :avatar

  process_in_background :avatar, url_with_processing: false
end

@user = User.new(avatar: File.new(...))
@user.save
@user.avatar.url #=> "/system/images/3/original/IMG_2772.JPG?1267562148"
@user.avatar.processing? #=> true
Delayed::Worker.new.work_off

@user.reload
@user.avatar.url #=> "/system/images/3/original/IMG_2772.JPG?1267562148"
@user.avatar.processing? #=> false
````

#### Only process certain styles

This is useful if you don’t want the background job to reprocess all
styles.

````ruby
class User < ActiveRecord::Base
  has_attached_file :avatar, styles: { small: "25x25#", medium: "50x50x" }

  process_in_background :avatar, only_process: [:small]
end
````

Like paperclip, you could also supply a lambda function to define
`only_process` dynamically.

````ruby
class User < ActiveRecord::Base
  has_attached_file :avatar, styles: { small: "25x25#", medium: "50x50x" }

  process_in_background :avatar, only_process: lambda { |a| a.instance.small_supported? ? [:small, :large] : [:large] }
end
````

#### Split processing

You can process some styles in the foreground and some in the background
by setting `only_process` on both `has_attached_file` and
`process_in_background`.

````ruby
class User < ActiveRecord::Base
  has_attached_file :avatar, styles: { small: "25x25#", medium: "50x50x" }, only_process: [:small]

  process_in_background :avatar, only_process: [:medium]
end
````

#### Reprocess Without Delay

This is useful if you don’t want the background job. It accepts
individual styles to. Take note, normal `reprocess!` does not accept styles as arguments anymore. It will delegate to DelayedPaperclip and
reprocess all styles.

````ruby
class User < ActiveRecord::Base
  has_attached_file :avatar, styles: { small: "25x25#", medium: "50x50x" }

  process_in_background :avatar
end

@user.avatar.url #=> "/system/images/3/original/IMG_2772.JPG?1267562148"
@user.avatar.reprocess_without_delay!(:medium)
````

Defaults
--------

Global defaults for all delayed_paperclip instances in your app can be
defined by changing the DelayedPaperclip.options Hash, this can be useful for setting a default ‘processing image,’ so you won’t have to define it in every `process_in_background` definition.

If you’re using Rails you can define a Hash with default options in
config/application.rb or in any of the config/environments/\*.rb files on `config.delayed_paperclip_defaults`, these will get merged into DelayedPaperclip.options as your Rails app boots. An example:

````
module YourApp
  class Application < Rails::Application
    # Other code...

    config.delayed_paperclip_defaults = {
        url_with_processing: true,
        processing_image_url: 'custom_processing.png'
    }
  end
end
````

What if I’m not using images?
-----------------------------

This library works no matter what kind of post-processing you are doing
with Paperclip.

Does it work with s3?
---------------------

Yes.

Contributing
------------

Checkout out CONTRIBUTING. In short, you’ll need a redis server running
for testing. Run all tests with

````
# Rspec on all versions
rake appraisal spec
````