Ruby on Rails 3 教程的错误，第 13 章

Question

我将 Rails 3 教程中的“示例应用程序”更新到了 Rails 3.1。一切都很顺利，除了当我使用该网站并且登录用户尝试关注/取消关注另一个用户时，我从日志中收到以下消息：

Started POST "/relationships" for 127.0.0.1 at 2011-09-29 20:06:30 -0400
  Processing by RelationshipsController#create as JS
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"Yn4XSU4RSEjGqpv1H/ZAxTAi/5JREDaBaa5UbPArRAo=", "relationship"=>{"followed_id"=>"7"}, "commit"=>"Follow"}
  User Load (0.1ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 101 LIMIT 1
  User Load (0.2ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1  [["id", "7"]]
  SQL (3.5ms)  INSERT INTO "relationships" ("created_at", "followed_id", "follower_id", "updated_at") VALUES (?, ?, ?, ?)  [["created_at", Fri, 30 Sep 2011 00:06:30 UTC +00:00], ["followed_id", 7], ["follower_id", 101], ["updated_at", Fri, 30 Sep 2011 00:06:30 UTC +00:00]]
  Relationship Load (0.2ms)  SELECT "relationships".* FROM "relationships" WHERE "relationships"."follower_id" = 101 AND "relationships"."followed_id" = 7 LIMIT 1
Rendered users/_unfollow.html.erb (3.5ms)
   (0.2ms)  SELECT COUNT(*) FROM "users" INNER JOIN "relationships" ON "users"."id" = "relationships"."follower_id" WHERE "relationships"."followed_id" = 7
Rendered relationships/create.js.erb (6.7ms)
Completed 200 OK in 51ms (Views: 12.1ms | ActiveRecord: 4.7ms)


Started POST "/relationships" for 127.0.0.1 at 2011-09-29 20:06:31 -0400
  Processing by RelationshipsController#create as JS
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"Yn4XSU4RSEjGqpv1H/ZAxTAi/5JREDaBaa5UbPArRAo=", "relationship"=>{"followed_id"=>"7"}, "commit"=>"Follow"}
  User Load (0.1ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 101 LIMIT 1
  User Load (0.2ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1  [["id", "7"]]
  SQL (0.6ms)  INSERT INTO "relationships" ("created_at", "followed_id", "follower_id", "updated_at") VALUES (?, ?, ?, ?)  [["created_at", Fri, 30 Sep 2011 00:06:31 UTC +00:00], ["followed_id", 7], ["follower_id", 101], ["updated_at", Fri, 30 Sep 2011 00:06:31 UTC +00:00]]
SQLite3::ConstraintException: constraint failed: INSERT INTO "relationships" ("created_at", "followed_id", "follower_id", "updated_at") VALUES (?, ?, ?, ?)
Completed 500 Internal Server Error in 35ms

SQLite3::ConstraintException (columns follower_id, followed_id are not unique):

该操作应该有效，因为这是我第一次创建该关联。发生该错误后，我需要重新启动服务器才能返回到我的用户，否则服务器会继续抛出异常。这是一个示例：

Rendered /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/actionpack-3.1.0/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.0ms)
Rendered /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/actionpack-3.1.0/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (0.9ms)
Rendered /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/actionpack-3.1.0/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (3.7ms)
[2011-09-29 20:08:12] ERROR SQLite3::Exception: cannot use a closed statement
    /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/activerecord-3.1.0/lib/active_record/connection_adapters/sqlite_adapter.rb:110:in `close'
    /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/activerecord-3.1.0/lib/active_record/connection_adapters/sqlite_adapter.rb:110:in `block in clear_cache!'
    /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/activerecord-3.1.0/lib/active_record/connection_adapters/sqlite_adapter.rb:110:in `each'
    /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/activerecord-3.1.0/lib/active_record/connection_adapters/sqlite_adapter.rb:110:in `clear_cache!'
    /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/activerecord-3.1.0/lib/active_record/connection_adapters/sqlite_adapter.rb:104:in `disconnect!'
    /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:214:in `block in clear_reloadable_connections!'
    /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:213:in `each'
    /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:213:in `clear_reloadable_connections!'
    /Users/huguesjoly/.rvm/gems/ruby-1.9.2-p180    rails3tutorial/gems/activesupport-3.1.0/lib/active_support/core_ext/module/synchronization.rb:35:in `block in clear_reloadable_connections_with_synchronization!'
    ...

因此，重新启动后回到我的用户，我可以看到记录已经创建。但是，如果我尝试删除该关系，我会从该日志文件中收到以下错误：

Started  DELETE "/relationships/95" for 127.0.0.1 at 2011-09-29 20:11:59 -0400
 Processing by RelationshipsController#destroy as JS
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"7YfmrROy4dqviuRakYSyWz2xZLbqIBwfU5McvqBWBrU=", "commit"=>"Unfollow", "id"=>"95"}
  User Load (0.1ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 101 LIMIT 1
  Relationship Load (0.1ms)  SELECT "relationships".* FROM "relationships" WHERE "relationships"."id" = ? LIMIT 1  [["id", "95"]]
  User Load (0.1ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 7 LIMIT 1
  Relationship Load (0.1ms)  SELECT "relationships".* FROM "relationships" WHERE "relationships"."follower_id" = 101 AND "relationships"."followed_id" = 7 LIMIT 1
  SQL (0.3ms)  DELETE FROM "relationships" WHERE "relationships"."id" = ?  [["id", 95]]
Rendered users/_follow.html.erb (2.0ms)
   (0.2ms)  SELECT COUNT(*) FROM "users" INNER JOIN "relationships" ON "users"."id" = "relationships"."follower_id" WHERE "relationships"."followed_id" = 7
Rendered relationships/destroy.js.erb (5.3ms)
Completed 200 OK in 68ms (Views: 32.5ms | ActiveRecord: 1.5ms)


Started DELETE "/relationships/95" for 127.0.0.1 at 2011-09-29 20:11:59 -0400
  Processing by RelationshipsController#destroy as JS
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"7YfmrROy4dqviuRakYSyWz2xZLbqIBwfU5McvqBWBrU=", "commit"=>"Unfollow", "id"=>"95"}
  User Load (0.1ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 101 LIMIT 1
  Relationship Load (0.1ms)  SELECT "relationships".* FROM "relationships" WHERE "relationships"."id" = ? LIMIT 1  [["id", "95"]]
Completed 404 Not Found in 28ms

ActiveRecord::RecordNotFound (Couldn't find Relationship with id=95):
  app/controllers/relationships_controller.rb:24:in `destroy'

再次，如果我返回用户页面，我可以看到该关系已被删除。看起来好像无缘无故地抛出了异常。事实上，如果我重新规范测试以下/追随者关系，一切都会正常工作。此外，使用rails 3.0的sample_app版本运行得很好。

有没有可能其中一个 gem 在 Rails 3.1 的上下文中存在错误？这是我的 Gemfile 列表，以防有帮助：

source 'http://rubygems.org'

gem 'rails', '3.1.0'

# Bundle edge Rails instead:
# gem 'rails',     :git => 'git://github.com/rails/rails.git'

gem 'gravatar_image_tag', '1.0.0'
gem 'will_paginate', '3.0.1'
gem 'sqlite3', '1.3.4'


# Gems used only for assets and not required
# in production environments by default.
group :assets do
  gem 'sass-rails', "  ~> 3.1.0"
  gem 'coffee-rails', "~> 3.1.1"
  gem 'uglifier'
end

# Is replacing: gem 'prototype-rails'
gem 'jquery-rails'

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

# Deploy with Capistrano
# gem 'capistrano'

# To use debugger
# gem 'ruby-debug19', :require => 'ruby-debug'

group :development do
  gem 'rspec-rails', '2.6.1'
  gem 'annotate', '2.4.0'
  gem 'faker', '1.0.0'
end

group :test do
  gem 'rspec-rails', '2.6.1'
  gem 'webrat', '0.7.3'
  gem 'spork', '0.8.5'
  gem 'factory_girl_rails', '1.2.0'

  # Pretty printed test output
  gem 'turn', :require => false
end

提前致谢，

Answer 1

我在 Ajax 实现部分遇到了这个问题。问题是因为本教程是为 Prototype（Rails 3.1 之前的版本）编写的，但 Rails 3.1 使用 JQuery。

这是 JQuery 代码

create.js.erb

$("#follow_form").html("<%= escape_javascript(render('users/unfollow')) %>");
$("#followers").html('<%= "#{@user.followers.count} followers" %>'); 

destroy.js.erb

$("#follow_form").html("<%= escape_javascript(render('users/follow')) %>"");
$("#followers").html('<%= "#{@user.followers.count} followers" %>'); 

源

Answer 2

这是一个迟到的答案，我在阅读教程时遇到了同样的问题。

检查您的 Rsepc 测试是否有 AbstractController::DoubleRenderError 失败。如果是这样，您可能忘记在添加 respond_to 块后删除 RelationbshipsController 中的 redirect_to @user 行。