Ruby on rails 未定义的方法“键”和#x27；对于nil:nilclasserubyonrails

我正在使用以下[Rails教程][1]

[1] ：学习并进入我链接的部分

当我访问REST URL xxx/users/1时，我得到错误信息：

NoMethodError in UsersController#index
undefined method `key?' for nil:NilClass

actionpack (3.2.8) lib/action_controller/metal/hide_actions.rb:36:in `visible_action?'
actionpack (3.2.8) lib/action_controller/metal/hide_actions.rb:18:in `method_for_action'
actionpack (3.2.8) lib/action_controller/metal/implicit_render.rb:14:in `method_for_action'
actionpack (3.2.8) lib/action_controller/metal/compatibility.rb:61:in `method_for_action'
actionpack (3.2.8) lib/abstract_controller/base.rb:115:in `process'
actionpack (3.2.8) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.2.8) lib/action_controller/metal.rb:203:in `dispatch'
actionpack (3.2.8) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.2.8) lib/action_controller/metal.rb:246:in `block in action'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:73:in `call'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:36:in `call'
journey (1.0.4) lib/journey/router.rb:68:in `block in call'
journey (1.0.4) lib/journey/router.rb:56:in `each'
journey (1.0.4) lib/journey/router.rb:56:in `call'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:600:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.4.1) lib/rack/etag.rb:23:in `call'
rack (1.4.1) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/flash.rb:242:in `call'
rack (1.4.1) lib/rack/session/abstract/id.rb:205:in `context'
rack (1.4.1) lib/rack/session/abstract/id.rb:200:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/cookies.rb:339:in `call'
activerecord (3.2.8) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.2.8) lib/active_record/connection_adapters/abstract/connection_pool.rb:473:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `_run__4595614879947811243__call__2349863385936106112__callbacks'
activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.8) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
activesupport (3.2.8) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.8) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/reloader.rb:65:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
railties (3.2.8) lib/rails/rack/logger.rb:26:in `call_app'
railties (3.2.8) lib/rails/rack/logger.rb:16:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/request_id.rb:22:in `call'
rack (1.4.1) lib/rack/methodoverride.rb:21:in `call'
rack (1.4.1) lib/rack/runtime.rb:17:in `call'
activesupport (3.2.8) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.4.1) lib/rack/lock.rb:15:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/static.rb:62:in `call'
railties (3.2.8) lib/rails/engine.rb:479:in `call'
railties (3.2.8) lib/rails/application.rb:223:in `call'
rack (1.4.1) lib/rack/content_length.rb:14:in `call'
rack (1.4.1) lib/rack/handler/webrick.rb:59:in `service'
/usr/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
/usr/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
/usr/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'

通过在线阅读，我认为这与用户模型中的代码有关，但我一直遵循tut，我的代码似乎与原始代码相同。但也许其他人能看到我遗漏的东西：

class User < ActiveRecord::Base
  attr_accessible :email, :name, :password, :password_confirmation
  has_secure_password

  before_save { |user| user.email = email.downcase }

  validates :name, presence: true, length: { maximum: 50 }
  VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i
  validates :email, presence: true, format: { with: VALID_EMAIL_REGEX }, uniqueness: { case_sensitive: false }
  validates :password, presence: true, length: { minimum: 6 }
  validates :password_confirmation, presence: true
end

再次编辑：以下是用户\u controller.rb的内容。这可能是问题所在，但教程中列出了：

class UsersController < ApplicationController
  def show
    @user = user.find(params[:id])
  end

  def new
  end
end

class UsersController

重新启动Rails服务器修复了该问题！谢谢

是否有带有错误消息的stacktrace？请检查您是否在routes.rb中定义了“resources:users”，以及是否有操作索引、显示、。。。在控制器中声明您可以显示控制器代码吗？我知道错误不是由您拥有的代码引起的，而是由您没有的代码引起的。正如@user1829889所建议的，向您的控制器添加索引操作谢谢大家。只是想让你知道重启Rails服务器修复了这个问题！