rails_admin + paperclip

Gemfile

# Gemfile
gem 'rails_admin'
gem 'paperclip'

product.rb

# models/product.rb
class Product < ActiveRecord::Base
  has_attached_file :logo,
    styles: {
      thumb: "100x100#",
      small: "150x150>",
      square: '200x200#',
      medium: "200x200" },
    url: "/logos/:style/:hash.:extension",
    hash_secret: "longSecretString",
    default_url: "/logos/no-image-available.png"
    # url: ":rails_root/public/photos/images/:id/:style/:basename.:extension"

  validates_attachment :logo, :presence => true,
    content_type: { content_type: "image/jpeg" },
    size: { in: 0..2.megabytes }

  rails_admin do
    label 'Товары'

    field :logo, :paperclip
  end
end