Question

我在控制台中运行命令rails server -p 8000以启动我的rails应用程序，然后我在浏览器中访问了localhost：8000，但是我收到错误消息说出错了。我检查了我的控制台，我看到了这个：

Started GET "/" for 127.0.0.1 at 2015-08-15 14:21:23 -0400

NameError (uninitialized constant ActiveModel::Validations::PresenceValidator):
  activerecord (4.2.3) lib/active_record/validations/presence.rb:3:in `<module:Validations>'
  activerecord (4.2.3) lib/active_record/validations/presence.rb:2:in `<module:ActiveRecord>'
  activerecord (4.2.3) lib/active_record/validations/presence.rb:1:in `<top (required)>'
  activerecord (4.2.3) lib/active_record/validations.rb:90:in `<top (required)>'
  activerecord (4.2.3) lib/active_record/base.rb:294:in `<class:Base>'
  activerecord (4.2.3) lib/active_record/base.rb:269:in `<module:ActiveRecord>'
  activerecord (4.2.3) lib/active_record/base.rb:26:in `<top (required)>'
  activerecord (4.2.3) lib/active_record/migration.rb:383:in `connection'
  activerecord (4.2.3) lib/active_record/migration.rb:370:in `call'
  actionpack (4.2.3) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
  activesupport (4.2.3) lib/active_support/callbacks.rb:84:in `run_callbacks'
  actionpack (4.2.3) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (4.2.3) lib/action_dispatch/middleware/reloader.rb:73:in `call'
  actionpack (4.2.3) lib/action_dispatch/middleware/remote_ip.rb:78:in `call'
  actionpack (4.2.3) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  actionpack (4.2.3) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.2.3) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.2.3) lib/rails/rack/logger.rb:20:in `block in call'
  activesupport (4.2.3) lib/active_support/tagged_logging.rb:68:in `block in tagged'
  activesupport (4.2.3) lib/active_support/tagged_logging.rb:26:in `tagged'
  activesupport (4.2.3) lib/active_support/tagged_logging.rb:68:in `tagged'
  railties (4.2.3) lib/rails/rack/logger.rb:20:in `call'
  actionpack (4.2.3) lib/action_dispatch/middleware/request_id.rb:21:in `call'
  rack (1.6.4) lib/rack/methodoverride.rb:22:in `call'
  rack (1.6.4) lib/rack/runtime.rb:18:in `call'
  activesupport (4.2.3) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'
  rack (1.6.4) lib/rack/lock.rb:17:in `call'
  actionpack (4.2.3) lib/action_dispatch/middleware/static.rb:116:in `call'
  rack (1.6.4) lib/rack/sendfile.rb:113:in `call'
  railties (4.2.3) lib/rails/engine.rb:518:in `call'
  railties (4.2.3) lib/rails/application.rb:165:in `call'
  rack (1.6.4) lib/rack/lock.rb:17:in `call'
  rack (1.6.4) lib/rack/content_length.rb:15:in `call'
  rack (1.6.4) lib/rack/handler/webrick.rb:88:in `service'
  c:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
  c:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
  c:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'

我昨天更新了所有宝石，包括rails，所以我认为它与它有关。当我更新所有宝石时，有什么我做错了吗？我运行了命令，然后我更新了Gemfile，但是我错过了什么吗？（如果你想让我把Gemfile放在这里，请告诉我）这是我的Gemfile

source 'https://rubygems.org'


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.1'
# Use sqlite3 as the database for Active Record
gem 'sqlite3'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 4.0.3'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .js.coffee assets and views
gem 'coffee-rails', '~> 4.0.0'
# See https://github.com/sstephenson/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', '~> 2.0'
# bundle exec rake doc:rails generates the API under doc/api.
gem 'sdoc', '~> 0.4.0',          group: :doc

# Use ActiveModel has_secure_password
gem 'bcrypt', '~> 3.1.7'

# Use unicorn as the app server
# gem 'unicorn'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

# Use debugger
# gem 'debugger', group: [:development, :test]

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin]

# Scans for vulnerabilities
gem 'brakeman',  '~> 3.0.5'

gem 'dawnscanner', '~> 1.3.5'

Answer 1

你必须要求整个active_model，因为它使用自动加载到＆＃34; lazily require＆＃34;根据需要上课。

以下代码可以正常使用：

require 'active_model'


class Person
  include ActiveModel::Validations
end

Answer 2

我想我弄明白了这个问题。我做了一个新的应用程序，没有两个宝石，它工作。我去了我的应用程序并取出了一个宝石（dawnscanner）并且它有效。

运行rails服务器时的NameError

2 个答案: