我正在关注导轨教程@ http://railstutorial.org
在第11章，我遇到了显示用户微博的问题。
根据教程，RSPEC测试应该通过。但是，它失败了
1) UsersController GET 'show' should show the user's microposts
Failure/Error: get :show, :id => @user
undefined method `model_name' for NilClass:Class
# ./app/views/users/show.html.erb:10:in `_app_views_users_show_html_erb__49
# ./spec/controllers/users_controller_spec.rb:71
当我尝试访问与其关联的微博的用户页面时，我得到一个例外：
NoMethodError in Users#show
Showing C:/Documents and Settings/XXXXX/workspace/sample_app/app/views/users/show.html.erb where line #10 raised:
undefined method `model_name' for NilClass:Class
Extracted source (around line #10):
7: </h1>
8: <% unless @user.microposts.empty? %>
9: <table class="microposts" summary="User microposts">
10: <%= render @microposts %>
11: </table>
12: <%= will_paginate @microposts %>
13: <% end %>
Rails.root: C:/Documents and Settings/XXXXX/workspace/sample_app
Application Trace | Framework Trace | Full Trace
actionpack (3.0.0) lib/action_view/render/partials.rb:319:in `partial_path'
actionpack (3.0.0) lib/action_view/render/partials.rb:207:in `setup'
actionpack (3.0.0) lib/action_view/render/partials.rb:186:in `initialize'
actionpack (3.0.0) lib/action_view/render/partials.rb:331:in `new'
actionpack (3.0.0) lib/action_view/render/partials.rb:331:in `_render_partial'
actionpack (3.0.0) lib/action_view/render/rendering.rb:31:in `render'
app/views/users/show.html.erb:10:in `_app_views_users_show_html_erb__49899798_36559632_0'
actionpack (3.0.0) lib/action_view/template.rb:135:in `send'
actionpack (3.0.0) lib/action_view/template.rb:135:in `render'
activesupport (3.0.0) lib/active_support/notifications.rb:54:in `instrument'
actionpack (3.0.0) lib/action_view/template.rb:127:in `render'
actionpack (3.0.0) lib/action_view/render/rendering.rb:59:in `_render_template'
activesupport (3.0.0) lib/active_support/notifications.rb:52:in `instrument'
activesupport (3.0.0) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.0.0) lib/active_support/notifications.rb:52:in `instrument'
actionpack (3.0.0) lib/action_view/render/rendering.rb:56:in `_render_template'
actionpack (3.0.0) lib/action_view/render/rendering.rb:26:in `render'
actionpack (3.0.0) lib/abstract_controller/rendering.rb:114:in `_render_template'
actionpack (3.0.0) lib/abstract_controller/rendering.rb:108:in `render_to_body'
actionpack (3.0.0) lib/action_controller/metal/renderers.rb:47:in `render_to_body'
actionpack (3.0.0) lib/action_controller/metal/compatibility.rb:55:in `render_to_body'
actionpack (3.0.0) lib/abstract_controller/rendering.rb:101:in `render_to_string'
actionpack (3.0.0) lib/abstract_controller/rendering.rb:92:in `render'
actionpack (3.0.0) lib/action_controller/metal/rendering.rb:17:in `render'
actionpack (3.0.0) lib/action_controller/metal/instrumentation.rb:40:in `render'
activesupport (3.0.0) lib/active_support/core_ext/benchmark.rb:5:in `ms'
c:/Ruby187/lib/ruby/1.8/benchmark.rb:308:in `realtime'
activesupport (3.0.0) lib/active_support/core_ext/benchmark.rb:5:in `ms'
actionpack (3.0.0) lib/action_controller/metal/instrumentation.rb:40:in `render'
actionpack (3.0.0) lib/action_controller/metal/instrumentation.rb:78:in `cleanup_view_runtime'
activerecord (3.0.0) lib/active_record/railties/controller_runtime.rb:15:in `cleanup_view_runtime'
actionpack (3.0.0) lib/action_controller/metal/instrumentation.rb:39:in `render'
actionpack (3.0.0) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
actionpack (3.0.0) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
actionpack (3.0.0) lib/abstract_controller/base.rb:150:in `process_action'
actionpack (3.0.0) lib/action_controller/metal/rendering.rb:11:in `process_action'
actionpack (3.0.0) lib/abstract_controller/callbacks.rb:18:in `process_action'
activesupport (3.0.0) lib/active_support/callbacks.rb:435:in `_run__434435962__process_action__453433196__callbacks'
activesupport (3.0.0) lib/active_support/callbacks.rb:409:in `send'
activesupport (3.0.0) lib/active_support/callbacks.rb:409:in `_run_process_action_callbacks'
activesupport (3.0.0) lib/active_support/callbacks.rb:93:in `send'
activesupport (3.0.0) lib/active_support/callbacks.rb:93:in `run_callbacks'
actionpack (3.0.0) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.0.0) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
activesupport (3.0.0) lib/active_support/notifications.rb:52:in `instrument'
activesupport (3.0.0) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.0.0) lib/active_support/notifications.rb:52:in `instrument'
actionpack (3.0.0) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.0.0) lib/action_controller/metal/rescue.rb:17:in `process_action'
actionpack (3.0.0) lib/abstract_controller/base.rb:119:in `process'
actionpack (3.0.0) lib/abstract_controller/rendering.rb:40:in `process'
actionpack (3.0.0) lib/action_controller/metal.rb:133:in `dispatch'
actionpack (3.0.0) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.0.0) lib/action_controller/metal.rb:173
actionpack (3.0.0) lib/action_dispatch/routing/route_set.rb:62:in `call'
actionpack (3.0.0) lib/action_dispatch/routing/route_set.rb:62:in `dispatch'
actionpack (3.0.0) lib/action_dispatch/routing/route_set.rb:27:in `call'
rack-mount (0.6.13) lib/rack/mount/route_set.rb:148:in `call'
rack-mount (0.6.13) lib/rack/mount/code_generation.rb:93:in `recognize'
rack-mount (0.6.13) lib/rack/mount/code_generation.rb:82:in `optimized_each'
rack-mount (0.6.13) lib/rack/mount/code_generation.rb:92:in `recognize'
rack-mount (0.6.13) lib/rack/mount/route_set.rb:139:in `call'
actionpack (3.0.0) lib/action_dispatch/routing/route_set.rb:492:in `call'
actionpack (3.0.0) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
actionpack (3.0.0) lib/action_dispatch/middleware/head.rb:14:in `call'
rack (1.2.1) lib/rack/methodoverride.rb:24:in `call'
actionpack (3.0.0) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.0.0) lib/action_dispatch/middleware/flash.rb:182:in `call'
actionpack (3.0.0) lib/action_dispatch/middleware/session/abstract_store.rb:149:in `call'
actionpack (3.0.0) lib/action_dispatch/middleware/cookies.rb:287:in `call'
activerecord (3.0.0) lib/active_record/query_cache.rb:32:in `call'
activerecord (3.0.0) lib/active_record/connection_adapters/abstract/query_cache.rb:28:in `cache'
activerecord (3.0.0) lib/active_record/query_cache.rb:12:in `cache'
activerecord (3.0.0) lib/active_record/query_cache.rb:31:in `call'
activerecord (3.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:355:in `call'
actionpack (3.0.0) lib/action_dispatch/middleware/callbacks.rb:46:in `call'
activesupport (3.0.0) lib/active_support/callbacks.rb:415:in `_run_call_callbacks'
actionpack (3.0.0) lib/action_dispatch/middleware/callbacks.rb:44:in `call'
rack (1.2.1) lib/rack/sendfile.rb:107:in `call'
actionpack (3.0.0) lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
actionpack (3.0.0) lib/action_dispatch/middleware/show_exceptions.rb:46:in `call'
railties (3.0.0) lib/rails/rack/logger.rb:13:in `call'
rack (1.2.1) lib/rack/runtime.rb:17:in `call'
activesupport (3.0.0) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.2.1) lib/rack/lock.rb:11:in `call'
rack (1.2.1) lib/rack/lock.rb:11:in `synchronize'
rack (1.2.1) lib/rack/lock.rb:11:in `call'
actionpack (3.0.0) lib/action_dispatch/middleware/static.rb:30:in `call'
railties (3.0.0) lib/rails/application.rb:168:in `call'
railties (3.0.0) lib/rails/application.rb:77:in `send'
railties (3.0.0) lib/rails/application.rb:77:in `method_missing'
railties (3.0.0) lib/rails/rack/log_tailer.rb:14:in `call'
rack (1.2.1) lib/rack/content_length.rb:13:in `call'
rack (1.2.1) lib/rack/handler/webrick.rb:52:in `service'
c:/Ruby187/lib/ruby/1.8/webrick/httpserver.rb:104:in `service'
c:/Ruby187/lib/ruby/1.8/webrick/httpserver.rb:65:in `run'
c:/Ruby187/lib/ruby/1.8/webrick/server.rb:173:in `start_thread'
c:/Ruby187/lib/ruby/1.8/webrick/server.rb:162:in `start'
c:/Ruby187/lib/ruby/1.8/webrick/server.rb:162:in `start_thread'
c:/Ruby187/lib/ruby/1.8/webrick/server.rb:95:in `start'
c:/Ruby187/lib/ruby/1.8/webrick/server.rb:92:in `each'
c:/Ruby187/lib/ruby/1.8/webrick/server.rb:92:in `start'
c:/Ruby187/lib/ruby/1.8/webrick/server.rb:23:in `start'
c:/Ruby187/lib/ruby/1.8/webrick/server.rb:82:in `start'
rack (1.2.1) lib/rack/handler/webrick.rb:13:in `run'
rack (1.2.1) lib/rack/server.rb:213:in `start'
railties (3.0.0) lib/rails/commands/server.rb:65:in `start'
railties (3.0.0) lib/rails/commands.rb:30
railties (3.0.0) lib/rails/commands.rb:27:in `tap'
railties (3.0.0) lib/rails/commands.rb:27
script/rails:6:in `require'
script/rails:6
Request
Parameters:
{"id"=>"1"}
Show session dump
Show env dump
Response
Headers:
None
我试图找到有类似问题的人，但无济于事。
我已经重新编写了本章的整个代码，以确保它不是拼写错误，仍然没有帮助。
感谢您给予的任何帮助。
答案 0 :(得分：5)
我遇到了同样的问题......花了一段时间才弄明白。 我有两个在UsersController中定义的show方法实例。一旦我删除了那个不包含@microposts声明的声明，（第二个没有@microposts声明），测试按预期运行，页面正确地渲染了微博。
干杯！ 一个