```ruby
class ListingImage < ActiveRecord::Base
  belongs_to :listing

  has_attached_file :image, 
    :storage => :s3, 
    :s3_credentials => "#{Rails.root}/config/s3.yml", 
    :path => ":id/:style/:filename"

  before_save :set_complete_image_url

  def set_complete_image_url
    self.complete_image_url = image_url
  end

  def image_url
    self.image.url
  end
end
```

Make S3 images readable by default
user
```ruby
class ListingImage < ActiveRecord::Base
  belongs_to :listing

  has_attached_file :image, 
    :storage => :s3, 
    :s3_credentials => "#{Rails.root}/config/s3.yml", 
    :path => ":id/:style/:filename",
    :s3_permissions => :public_read

  before_save :set_complete_image_url

  def set_complete_image_url
    self.complete_image_url = image_url
  end

  def image_url
    self.image.url
  end
end
```
assistant