radrails开发服务器启动错误：load_missing_constant

Question

Here is the stacktrace I get in the console:

 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

It was fine before. I've made no env change(that i remember). Very strange. I am running RadRails on a Windows Vista machine.

Answer 1

If you get the error:

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

Then it means you have not installed the activerecord ruby gem. You need to install the gem so that Aptana can find it, so you need to learn about the following procedures:

1. Listing remotely installable gems.
2. Searching remotely installable gems.
3. Installing a remote gem.
4. Verifying your gem is installed.

Read all this: http://docs.rubygems.org/read/chapter/2

To remedy the above error, here is what you have to do:

Open a command prompt and run these commands in the terminal:

#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  

Restart your IDE. Aptana needs to be told to use your activerecord gem:

require 'active_record';

Here is some code that uses the ActiveRecord gem to see if Aptana can find your activerecord gem:

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

This produces no error and prints "activerecord gem is installed";

Answer 2

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