example.rb

class AdImageHandler
  attr_reader :model, :data, :file_path, :file_name

  def initialize(model, data, image_index)
    @model = model
    @data = data
    @file_name = SecureRandom.uuid
    @file_path = AdImageHandler.generate_image_path(@file_name)
    @image_index = image_index
  end

  def write_initial_file
    uri = URI::Data.new(@data)

    File.open @file_path, 'wb' do |file|
      file.write(uri.data)
    end
  end

  def resize_image_file
    MiniMagick::Tool::Mogrify.new do |m|
      m.format 'png'
      m << @file_path
    end
  end

  def clean_old_file
    old_file_name = @model.base_images[@image_index]
    old_file_path = AdImageHandler.generate_image_path(old_file_name)

    if File.exist?(old_file_path)
      File.delete(old_file_path)
    end
  end

  def save_image_to_model
    @model.base_images[@image_index] = @file_name
  end

  def save
    write_initial_file
    resize_image_file
    clean_old_file
    save_image_to_model
  end


  class << self
    def generate_image_path(name)
      "#{ENV['HOME']}/images/#{name}.png"
    end
  end
end

class Controller
  def upload_images
    data = params["image_#{index}"]
    if data
      img_handler = AdImageHandler.new(@ad, data, index)
      img_handler.save
    end
  end
end