我创建了一个简单的rails应用程序，当我运行rails s时。它会发出这一堆错误：-s我试图重新安装activerecord但它无法解决问题。此外，我尝试使用rvm删除所有gemset并重新安装，但它仍然是相同的。
/usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/connection_adapters/abstract/connection_specification.rb:33:in `resolve_string_connection': undefined method `fetch' for false:FalseClass (NoMethodError)
from /usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/connection_adapters/abstract/connection_specification.rb:23:in `spec'
from /usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/connection_adapters/abstract/connection_specification.rb:127:in `establish_connection'
from /usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/railtie.rb:76:in `block (2 levels) in <class:Railtie>'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/lazy_load_hooks.rb:36:in `instance_eval'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/lazy_load_hooks.rb:36:in `execute_hook'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/lazy_load_hooks.rb:26:in `block in on_load'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/lazy_load_hooks.rb:25:in `each'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/lazy_load_hooks.rb:25:in `on_load'
from /usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/railtie.rb:74:in `block in <class:Railtie>'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/initializable.rb:30:in `instance_exec'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/initializable.rb:30:in `run'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/initializable.rb:55:in `block in run_initializers'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/initializable.rb:54:in `each'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/initializable.rb:54:in `run_initializers'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/application.rb:136:in `initialize!'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/railtie/configurable.rb:30:in `method_missing'
from /home/vic4ever/crowdvn/crowd.vn/config/environment.rb:5:in `<top (required)>'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:251:in `require'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:251:in `block in require'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:236:in `load_dependency'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:251:in `require'
from /home/vic4ever/crowdvn/crowd.vn/config.ru:4:in `block in <main>'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/builder.rb:51:in `instance_eval'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/builder.rb:51:in `initialize'
from /home/vic4ever/crowdvn/crowd.vn/config.ru:1:in `new'
from /home/vic4ever/crowdvn/crowd.vn/config.ru:1:in `<main>'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/builder.rb:40:in `eval'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/builder.rb:40:in `parse_file'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/server.rb:200:in `app'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands/server.rb:46:in `app'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/server.rb:301:in `wrapped_app'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/server.rb:252:in `start'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands/server.rb:70:in `start'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands.rb:55:in `block in <top (required)>'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands.rb:50:in `tap'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands.rb:50:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
答案 0 :(得分：2)
您需要一个数据库适配器（即config/database.yml）。
我会假设你使用Git进行源代码控制以保证自己的安全。它还可以帮助您查看按照以下说明进行的更改。
生成新的database.yml：
$ cd ~/path/to/my-existing-rails-app
$ rails new my-existing-rails-app --database=sqlite
一系列提示会询问您是否要创建/覆盖现有文件。继续对提示回答“否”，直到您看到要求创建config/database.yml的提示为止。如果您看到提示并回答“否”，则回答“是”。
如果您已在本地/开发环境中安装了--database=sqlite或--database=postgresql，则可以使用--database=mysql而不是--database=DATABASE。
更进一步，mysql
oracle
postgresql
sqlite3
frontbase
ibm_db
sqlserver
jdbcmysql
jdbcsqlite3
jdbcpostgresql
jdbc
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