SimplestPhoto

The easiest way to add photos to your Rails app and attach them to your models.

SimplestPhoto ...

• is dead simple to use
• is easy to change—migrations and models live in your app and you can do whatever you want to them
• caches your Dragonfly-processed images for you
• Requires Rails >= 5.1. For prior versions, use the 0.1.0 release.

How to use

1. Add it to your Gemfile and bundle install that thing.

2. Generate the Dragonfly config:

    rails generate dragonfly
   

3. Generate the models and migrations:

    rails generate simplest_photo
   

4. Do some rake db:migrate

5. Configure your models:

    class Dinosaur < ActiveRecord::Base
      extend SimplestPhoto::HasPhoto
   
      has_photo :hero, required: true
      has_photo :centerfold
    end
   

6. Update your Dragonfly config to generate PhotoCroppings:

    # config/initializers/dragonfly.rb
    Dragonfly.app.configure do
      SimplestPhoto::UrlHelper.install(self)
    end
   

How it works

Models

SimplestPhoto contains three models:

1. Photo: the core photo model, where the Dragonfly attachment actually happens.
2. PhotoAttachment: the join table that connects a Photo with the things it is attached to.
3. PhotoCropping: model used to cache processed images.

PhotoCropping needs a bit of explanation. When you ask Dragonfly for an image at 400x400#, it generates a unique job URL for that image. When that job URL is requested, Dragonfly does the processing, sends down the image, and then forgets about it. This is no good in production.

SimplestPhoto caches these processed photos by tapping into Dragonfly's URL method. When a new job comes in, SimplestPhoto checks for any PhotoCroppings with that job ID. If it finds one, it generates the URL to the stored image and sends that back. If it doesn't find one, it processes the image, stores it, inserts a new PhotoCropping record with that job ID, and sends down the processed image. The next time that job URL is generated, SimplestPhoto will use the stored image and skip the processing. Groovy.

Attachments

Suppose you have this model:

class Monster < ActiveRecord::Base
  extend SimplestPhoto::HasPhoto

  has_photo :headshot, required: true
end

SimplestPhoto generates this:

class Monster < ActiveRecord::Base
  extend SimplestPhoto::HasPhoto

  has_one :headshot_attachment,
          -> { where(attachable_name: :headshot) },
          as:         :attachable,
          class_name: 'PhotoAttachment',
          dependent:  :destroy

  has_one :headshot
          through: :headshot_attachment,
          source:  :photo

  validates :headshot, presence: true
end

Standard stuff. It also defines #headshot_id and #headshot_id= accessors, which are what you should use in a form:

f.input :headshot_id, collection: Photo.all

Customizations

To customize the valid image file extensions (which defaults to allowing .jpg, .jpeg, or .png extensions), override the valid_image_extensions method in the generated Photo model:

class Photo < ActiveRecord::Base
  def valid_image_extensions
    %w(jpg jpeg png gif)
  end
end

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