radrails开发服务器启动错误：load_missing_constant

Question

这是我在控制台中得到的stacktrace：

 C:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:443:in `load_missing_constant': uninitialized constant ActiveRecord (NameError)
    from C:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:80:in `const_missing'
    from C:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:92:in `const_missing'
    from C:/Users/rrevi/Documents/Aptana Studio/developer_portal/config/environment.rb:42
    from C:/ruby/lib/ruby/gems/1.8/gems/rails-2.3.2/lib/initializer.rb:111:in `run'
    from C:/Users/rrevi/Documents/Aptana Studio/developer_portal/config/environment.rb:9
    from C:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
    from C:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
    from C:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:156:in `require'
    from C:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:521:in `new_constants_in'
    from C:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:156:in `require'
    from C:/ruby/lib/ruby/gems/1.8/gems/rails-2.3.2/lib/commands/server.rb:84
    from C:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
    from C:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
    from ./script/server:3
    from -e:2:in `load'
    from -e:2

以前很好。 我没有做任何环境更改（我记得）。 很奇怪。 我在Windows Vista计算机上运行RadRails。

Answer 1

如果出现错误：

helloworld.rb:3:in `<main>': uninitialized constant ActiveRecord (NameError)

这意味着您尚未安装activerecord红宝石宝石。 您需要安装gem，以便Aptana可以找到它，因此您需要了解以下过程：

1. 列出可远程安装的gem。
2. 搜索可远程安装的gem。
3. 安装远程gem。
4. 验证您的gem已安装。

阅读所有内容： http : //docs.rubygems.org/read/chapter/2

要纠正上述错误，您需要执行以下操作：

打开命令提示符，然后在终端中运行以下命令：

#Find out what gems are installed on your computer:
gem query --local

#Take a look at the ActiveRecord gem, see if it is available.
gem query --remote --name-matches activerecord

#Get more info about the gem on the remote server.
gem specification --remote activerecord

#Install your gem:
gem install --remote activerecord

#See if it installed successfully and is in the installed gem list:
gem query --local  

重新启动您的IDE。 需要告知Aptana使用您的activerecord宝石：

require 'active_record';

以下是一些使用ActiveRecord gem的代码，以查看Aptana是否可以找到您的activerecord gem：

#Ruby code
require 'active_record'
class Dog < ActiveRecord::Base
  has_many :dog_tags
end
puts "activerecord gem is installed";

这不会产生任何错误，并显示“ ActiveRecord gem已安装”；

Answer 2

您正在运行过时的Rails版本，它表明您缺少ActiveRecord gem。