在没有设计的情况下为 rails_admin 定义 `current_user`答案

【问题标题】：define `current_user` for rails_admin without devise在没有设计的情况下为 rails_admin 定义 `current_user`
【发布时间】：2016-11-02 20:07:56
【问题描述】：

我正在尝试使用以下设置rails_admin

config.authorize_with :cancancan
config.current_user_method { current_user }

我没有使用devise，因为企业级 SSO 处理身份验证并将用户名传递给我。该应用只负责授权（cancancan）。我在ApplicationController 中有一个简单的current_user 实现：

def current_user
  user = User.find_by(:UserName => session[:user])
  return user
end

这对cancancan 来说效果很好，但rails_admin 不明白。我收到以下错误。我错过了什么？

NoMethodError (undefined method `new' for nil:NilClass): rails_admin (1.0.0) lib/rails_admin/config.rb:153:in `block in authorize_with' rails_admin (1.0.0) app/controllers/rails_admin/application_controller.rb:52:in `instance_eval' rails_admin (1.0.0) app/controllers/rails_admin/application_controller.rb:52:in `_authorize!' activesupport (4.2.7.1) lib/active_support/callbacks.rb:432:in `block in make_lambda' activesupport (4.2.7.1) lib/active_support/callbacks.rb:164:in `block in halting' activesupport (4.2.7.1) lib/active_support/callbacks.rb:504:in `block in call' activesupport (4.2.7.1) lib/active_support/callbacks.rb:504:in `each' activesupport (4.2.7.1) lib/active_support/callbacks.rb:504:in `call' activesupport (4.2.7.1) lib/active_support/callbacks.rb:92:in `__run_callbacks__' activesupport (4.2.7.1) lib/active_support/callbacks.rb:778:in `_run_process_action_callbacks' activesupport (4.2.7.1) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (4.2.7.1) lib/abstract_controller/callbacks.rb:19:in `process_action' actionpack (4.2.7.1) lib/action_controller/metal/rescue.rb:29:in `process_action' actionpack (4.2.7.1) lib/action_controller/metal/instrumentation.rb:32:in `block in process_action' activesupport (4.2.7.1) lib/active_support/notifications.rb:164:in `block in instrument' activesupport (4.2.7.1) lib/active_support/notifications/instrumenter.rb:20:in `instrument' activesupport (4.2.7.1) lib/active_support/notifications.rb:164:in `instrument' actionpack (4.2.7.1) lib/action_controller/metal/instrumentation.rb:30:in `process_action' actionpack (4.2.7.1) lib/action_controller/metal/params_wrapper.rb:250:in `process_action' activerecord (4.2.7.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action' actionpack (4.2.7.1) lib/abstract_controller/base.rb:137:in `process' actionview (4.2.7.1) lib/action_view/rendering.rb:30:in `process' actionpack (4.2.7.1) lib/action_controller/metal.rb:196:in `dispatch' actionpack (4.2.7.1) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch' actionpack (4.2.7.1) lib/action_controller/metal.rb:237:in `block in action' actionpack (4.2.7.1) lib/action_dispatch/routing/route_set.rb:74:in `dispatch' actionpack (4.2.7.1) lib/action_dispatch/routing/route_set.rb:43:in `serve' actionpack (4.2.7.1) lib/action_dispatch/journey/router.rb:43:in `block in serve' actionpack (4.2.7.1) lib/action_dispatch/journey/router.rb:30:in `each' actionpack (4.2.7.1) lib/action_dispatch/journey/router.rb:30:in `serve' actionpack (4.2.7.1) lib/action_dispatch/routing/route_set.rb:817:in `call' railties (4.2.7.1) lib/rails/engine.rb:518:in `call' railties (4.2.7.1) lib/rails/railtie.rb:194:in `public_send' railties (4.2.7.1) lib/rails/railtie.rb:194:in `method_missing' actionpack (4.2.7.1) lib/action_dispatch/routing/mapper.rb:51:in `serve' actionpack (4.2.7.1) lib/action_dispatch/journey/router.rb:43:in `block in serve' actionpack (4.2.7.1) lib/action_dispatch/journey/router.rb:30:in `each' actionpack (4.2.7.1) lib/action_dispatch/journey/router.rb:30:in `serve' actionpack (4.2.7.1) lib/action_dispatch/routing/route_set.rb:817:in `call' rack-pjax (1.0.0) lib/rack/pjax.rb:12:in `call' actionpack (4.2.7.1) lib/action_dispatch/middleware/flash.rb:260:in `call' rack (1.6.4) lib/rack/etag.rb:24:in `call' rack (1.6.4) lib/rack/conditionalget.rb:25:in `call' rack (1.6.4) lib/rack/head.rb:13:in `call' remotipart (1.3.1) lib/remotipart/middleware.rb:32:in `call' actionpack (4.2.7.1) lib/action_dispatch/middleware/params_parser.rb:27:in `call' actionpack (4.2.7.1) lib/action_dispatch/middleware/flash.rb:260:in `call' rack (1.6.4) lib/rack/session/abstract/id.rb:225:in `context' rack (1.6.4) lib/rack/session/abstract/id.rb:220:in `call' actionpack (4.2.7.1) lib/action_dispatch/middleware/cookies.rb:560:in `call' activerecord (4.2.7.1) lib/active_record/query_cache.rb:36:in `call' activerecord (4.2.7.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:653:in `call' activerecord (4.2.7.1) lib/active_record/migration.rb:377:in `call' actionpack (4.2.7.1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call' activesupport (4.2.7.1) lib/active_support/callbacks.rb:88:in `__run_callbacks__' activesupport (4.2.7.1) lib/active_support/callbacks.rb:778:in `_run_call_callbacks' activesupport (4.2.7.1) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (4.2.7.1) lib/action_dispatch/middleware/callbacks.rb:27:in `call' actionpack (4.2.7.1) lib/action_dispatch/middleware/reloader.rb:73:in `call' actionpack (4.2.7.1) lib/action_dispatch/middleware/remote_ip.rb:78:in `call' actionpack (4.2.7.1) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call' actionpack (4.2.7.1) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call' railties (4.2.7.1) lib/rails/rack/logger.rb:38:in `call_app' railties (4.2.7.1) lib/rails/rack/logger.rb:20:in `block in call' activesupport (4.2.7.1) lib/active_support/tagged_logging.rb:68:in `block in tagged' activesupport (4.2.7.1) lib/active_support/tagged_logging.rb:26:in `tagged' activesupport (4.2.7.1) lib/active_support/tagged_logging.rb:68:in `tagged' railties (4.2.7.1) lib/rails/rack/logger.rb:20:in `call' actionpack (4.2.7.1) 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 (4.2.7.1) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call' rack (1.6.4) lib/rack/lock.rb:17:in `call' actionpack (4.2.7.1) lib/action_dispatch/middleware/static.rb:120:in `call' rack (1.6.4) lib/rack/sendfile.rb:113:in `call' railties (4.2.7.1) lib/rails/engine.rb:518:in `call' railties (4.2.7.1) lib/rails/application.rb:165:in `call' rack (1.6.4) lib/rack/content_length.rb:15:in `call' puma (3.6.0) lib/puma/configuration.rb:225:in `call' puma (3.6.0) lib/puma/server.rb:578:in `handle_request' puma (3.6.0) lib/puma/server.rb:415:in `process_client' puma (3.6.0) lib/puma/server.rb:275:in `block in run' puma (3.6.0) lib/puma/thread_pool.rb:116:in `block in spawn_thread'

【问题讨论】：

标签： ruby-on-rails rails-admin cancancan

【解决方案1】：

在您的 ApplicationController 中尝试这样的操作：

def current_user
  @current_user ||= User.find(session[:user_id]) if session[:user_id]
end
helper_method :current_user

【讨论】：

感谢您的意见！我进行了更改并得到了同样的错误。
您的实际错误表明未定义方法 new 用于 nil 类。找出那个 nil 类是什么。在某处你打电话给.new 的东西是零。找到那个地方。

【解决方案2】：

在config/initializers/rails_admin.rb 中你必须添加authorize_with 方法：

config.authorize_with do
    authenticate_or_request_with_http_basic('Login required') do |username, password|
      user = User.where(email: username, admin: true).first
      user && user.authenticate(password)
    end
  end

完成后，您的用户将通过身份验证，您可以使用 current_user 变量

【讨论】：