所以我刚刚用HomeBrew安装了postgreSQL，并使用： rails new demo_app -d postgresql 命令初始化了我的新demo_app。
虽然我在启动服务器 rails s 时遇到以下错误。
SNIPPIT ：
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/postgresql_adapter.rb:1216:in `initialize': FATAL: role "demo" does not exist (PG::Error)
完整日志：
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/postgresql_adapter.rb:1216:in `initialize': FATAL: role "demo" does not exist (PG::Error)
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/postgresql_adapter.rb:1216:in `new'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/postgresql_adapter.rb:1216:in `connect'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/postgresql_adapter.rb:324:in `initialize'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `new'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `postgresql_connection'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_pool.rb:315:in `new_connection'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_pool.rb:325:in `checkout_new_connection'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_pool.rb:247:in `block (2 levels) in checkout'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_pool.rb:242:in `loop'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_pool.rb:242:in `block in checkout'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_pool.rb:239:in `checkout'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_pool.rb:102:in `block in connection'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_pool.rb:101:in `connection'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_pool.rb:410:in `retrieve_connection'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_specification.rb:171:in `retrieve_connection'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_specification.rb:145:in `connection'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/railtie.rb:88:in `block in <class:Railtie>'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/initializable.rb:30:in `instance_exec'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/initializable.rb:30:in `run'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/initializable.rb:55:in `block in run_initializers'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/initializable.rb:54:in `each'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/initializable.rb:54:in `run_initializers'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/application.rb:136:in `initialize!'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/railtie/configurable.rb:30:in `method_missing'
from /Users/anthonypanepinto/Sites/new_demo/demo/config/environment.rb:5:in `<top (required)>'
from /Users/anthonypanepinto/Sites/new_demo/demo/config.ru:3:in `require'
from /Users/anthonypanepinto/Sites/new_demo/demo/config.ru:3:in `block in <main>'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.5/lib/rack/builder.rb:51:in `instance_eval'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.5/lib/rack/builder.rb:51:in `initialize'
from /Users/anthonypanepinto/Sites/new_demo/demo/config.ru:in `new'
from /Users/anthonypanepinto/Sites/new_demo/demo/config.ru:in `<main>'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.5/lib/rack/builder.rb:40:in `eval'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.5/lib/rack/builder.rb:40:in `parse_file'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.5/lib/rack/server.rb:200:in `app'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/commands/server.rb:46:in `app'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.5/lib/rack/server.rb:304:in `wrapped_app'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.5/lib/rack/server.rb:254:in `start'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/commands/server.rb:70:in `start'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/commands.rb:55:in `block in <top (required)>'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/lib/rails/commands.rb:50:in `tap'
from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.13/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：3)