title: Paperclip::Errors::MissingRequiredValidatorError
body: <p>Sorry, but i cant found solution for my situation</p>
  
  <p>I have next code:</p>
  
  <pre><code>class Document &lt; ActiveRecord::Base
      has_attached_file :item,
                   content_type: { content_type: ["image/jpeg",    "image/gif", "document/pdf"] } 
  end
  </code></pre>
  
  <p>gemfile:</p>
  
  <pre><code>source 'https://rubygems.org'
  
  
  # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
  gem 'rails', '4.2.1'
  # Use sqlite3 as the database for Active Record
  gem 'sqlite3'
  # Use SCSS for stylesheets
  gem 'sass-rails', '~&gt; 5.0'
  # Use Uglifier as compressor for JavaScript assets
  gem 'uglifier', '&gt;= 1.3.0'
  # Use CoffeeScript for .coffee assets and views
  gem 'coffee-rails', '~&gt; 4.1.0'
  # See https://github.com/rails/execjs#readme for more supported runtimes
  # gem 'therubyracer', platforms: :ruby
  
  # Use jquery as the JavaScript library
  gem 'jquery-rails'
  # Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
  gem 'turbolinks'
  # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
  gem 'jbuilder', '~&gt; 2.0'
  # bundle exec rake doc:rails generates the API under doc/api.
  gem 'sdoc', '~&gt; 0.4.0', group: :doc
  
  gem 'bootstrap-sass'
  gem 'haml'
  
  gem "paperclip"
  # Use ActiveModel has_secure_password
  # gem 'bcrypt', '~&gt; 3.1.7'
  
  # Use Unicorn as the app server
  # gem 'unicorn'
  
  # Use Capistrano for deployment
  # gem 'capistrano-rails', group: :development
  </code></pre>
  
  <p>shema.db:</p>
  
  <p>ActiveRecord::Schema.define(version: 20151015113219) do</p>
  
  <pre><code>  create_table "documents", force: :cascade do |t|
      t.string   "title"
      t.datetime "created_at",        null: false
      t.datetime "updated_at",        null: false
      t.string   "item_file_name"
      t.string   "item_content_type"
      t.integer  "item_file_size"
      t.datetime "item_updated_at"
    end
  
  end
  </code></pre>
  
  <p>Documentscontroller:</p>
  
  <pre><code>class DocumentsController &lt; ApplicationController
      def index
      @documents = Document.order('created_at')
    end
  
    def new
      @document = Document.new
    end
  
    def create
      @document = Document.new(document_params)
      if @document.save
        flash[:success] = "The file was added!"
        redirect_to root_path
      else
        render 'new'
      end
    end
  
    private
  
    def document_params
      params.require(:document).permit(:item, :title)
    end
  end
  </code></pre>
  
  <p>When i unload new file, displaying error: <strong>Paperclip::Errors::MissingRequiredValidatorError</strong></p>
  
  <p>Full trace: </p>
  
  <pre><code>paperclip (4.3.1) lib/paperclip/attachment.rb:399:in `ensure_required_validations!'
  paperclip (4.3.1) lib/paperclip/attachment.rb:99:in `assign'
  paperclip (4.3.1) lib/paperclip/has_attached_file.rb:66:in `block in define_setter'
  activerecord (4.2.1) lib/active_record/attribute_assignment.rb:54:in `public_send'
  activerecord (4.2.1) lib/active_record/attribute_assignment.rb:54:in `_assign_attribute'
  activerecord (4.2.1) lib/active_record/attribute_assignment.rb:41:in `block in assign_attributes'
  actionpack (4.2.1) lib/action_controller/metal/strong_parameters.rb:183:in `each_pair'
  actionpack (4.2.1) lib/action_controller/metal/strong_parameters.rb:183:in `each_pair'
  activerecord (4.2.1) lib/active_record/attribute_assignment.rb:35:in `assign_attributes'
  activerecord (4.2.1) lib/active_record/core.rb:559:in `init_attributes'
  activerecord (4.2.1) lib/active_record/core.rb:281:in `initialize'
  activerecord (4.2.1) lib/active_record/inheritance.rb:61:in `new'
  activerecord (4.2.1) lib/active_record/inheritance.rb:61:in `new'
  actionpack (4.2.1) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
  actionpack (4.2.1) lib/abstract_controller/base.rb:198:in `process_action'
  actionpack (4.2.1) lib/action_controller/metal/rendering.rb:10:in `process_action'
  actionpack (4.2.1) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
  activesupport (4.2.1) lib/active_support/callbacks.rb:117:in `call'
  activesupport (4.2.1) lib/active_support/callbacks.rb:117:in `call'
  activesupport (4.2.1) lib/active_support/callbacks.rb:555:in `block (2 levels) in compile'
  activesupport (4.2.1) lib/active_support/callbacks.rb:505:in `call'
  activesupport (4.2.1) lib/active_support/callbacks.rb:505:in `call'
  activesupport (4.2.1) lib/active_support/callbacks.rb:92:in `_run_callbacks'
  activesupport (4.2.1) lib/active_support/callbacks.rb:776:in `_run_process_action_callbacks'
  activesupport (4.2.1) lib/active_support/callbacks.rb:81:in `run_callbacks'
  actionpack (4.2.1) lib/abstract_controller/callbacks.rb:19:in `process_action'
  actionpack (4.2.1) lib/action_controller/metal/rescue.rb:29:in `process_action'
  actionpack (4.2.1) lib/action_controller/metal/instrumentation.rb:32:in `block in process_action'
  activesupport (4.2.1) lib/active_support/notifications.rb:164:in `block in instrument'
  activesupport (4.2.1) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.2.1) lib/active_support/notifications.rb:164:in `instrument'
  actionpack (4.2.1) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  actionpack (4.2.1) lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
  activerecord (4.2.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  actionpack (4.2.1) lib/abstract_controller/base.rb:137:in `process'
  actionview (4.2.1) lib/action_view/rendering.rb:30:in `process'
  actionpack (4.2.1) lib/action_controller/metal.rb:196:in `dispatch'
  actionpack (4.2.1) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
  actionpack (4.2.1) lib/action_controller/metal.rb:237:in `block in action'
  actionpack (4.2.1) lib/action_dispatch/routing/route_set.rb:74:in `call'
  actionpack (4.2.1) lib/action_dispatch/routing/route_set.rb:74:in `dispatch'
  actionpack (4.2.1) lib/action_dispatch/routing/route_set.rb:43:in `serve'
  actionpack (4.2.1) lib/action_dispatch/journey/router.rb:43:in `block in serve'
  actionpack (4.2.1) lib/action_dispatch/journey/router.rb:30:in `each'
  actionpack (4.2.1) lib/action_dispatch/journey/router.rb:30:in `serve'
  actionpack (4.2.1) lib/action_dispatch/routing/route_set.rb:819:in `call'
  rack (1.6.1) lib/rack/etag.rb:24:in `call'
  rack (1.6.1) lib/rack/conditionalget.rb:38:in `call'
  rack (1.6.1) lib/rack/head.rb:13:in `call'
  actionpack (4.2.1) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
  actionpack (4.2.1) lib/action_dispatch/middleware/flash.rb:260:in `call'
  rack (1.6.1) lib/rack/session/abstract/id.rb:225:in `context'
  rack (1.6.1) lib/rack/session/abstract/id.rb:220:in `call'
  actionpack (4.2.1) lib/action_dispatch/middleware/cookies.rb:560:in `call'
  activerecord (4.2.1) lib/active_record/query_cache.rb:36:in `call'
  activerecord (4.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:649:in `call'
  activerecord (4.2.1) lib/active_record/migration.rb:378:in `call'
  actionpack (4.2.1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
  activesupport (4.2.1) lib/active_support/callbacks.rb:88:in `call'
  activesupport (4.2.1) lib/active_support/callbacks.rb:88:in `_run_callbacks'
  activesupport (4.2.1) lib/active_support/callbacks.rb:776:in `_run_call_callbacks'
  activesupport (4.2.1) lib/active_support/callbacks.rb:81:in `run_callbacks'
  actionpack (4.2.1) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (4.2.1) lib/action_dispatch/middleware/reloader.rb:73:in `call'
  actionpack (4.2.1) lib/action_dispatch/middleware/remote_ip.rb:78:in `call'
  actionpack (4.2.1) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  web-console (2.1.2) lib/web_console/middleware.rb:29:in `call'
  actionpack (4.2.1) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.2.1) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.2.1) lib/rails/rack/logger.rb:20:in `block in call'
  activesupport (4.2.1) lib/active_support/tagged_logging.rb:68:in `block in tagged'
  activesupport (4.2.1) lib/active_support/tagged_logging.rb:26:in `tagged'
  activesupport (4.2.1) lib/active_support/tagged_logging.rb:68:in `tagged'
  railties (4.2.1) lib/rails/rack/logger.rb:20:in `call'
  actionpack (4.2.1) lib/action_dispatch/middleware/request_id.rb:21:in `call'
  rack (1.6.1) lib/rack/methodoverride.rb:22:in `call'
  rack (1.6.1) lib/rack/runtime.rb:18:in `call'
  activesupport (4.2.1) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'
  rack (1.6.1) lib/rack/lock.rb:17:in `call'
  actionpack (4.2.1) lib/action_dispatch/middleware/static.rb:113:in `call'
  rack (1.6.1) lib/rack/sendfile.rb:113:in `call'
  railties (4.2.1) lib/rails/engine.rb:518:in `call'
  railties (4.2.1) lib/rails/application.rb:164:in `call'
  rack (1.6.1) lib/rack/lock.rb:17:in `call'
  rack (1.6.1) lib/rack/content_length.rb:15:in `call'
  rack (1.6.1) lib/rack/handler/webrick.rb:89:in `service'
  /usr/local/rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/webrick/httpserver.rb:138:in `service'
  /usr/local/rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/webrick/httpserver.rb:94:in `run'
  /usr/local/rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/webrick/server.rb:294:in `block in start_thread' 
  </code></pre>