我正在阅读tekpubrack教程，但是当我尝试在rack中运行一个基本程序时，我遇到了这个错误。ERRORRack::Lint::LintError:Responsebodymustrespondtoeach/Users/adam/.rvm/gems/ruby-1.9.3-preview1/gems/rack-1.3.4/lib/rack/lint.rb:19:in`assert'/Users/adam/.rvm/gems/ruby-1.9.3-preview1/gems/rack-1.3.4/lib/rack/lint.rb:513:in`each'/Users/adam/.rvm

我将DataMappergem与Sinatra一起使用，并按照此处的教程进行操作:http://net.tutsplus.com/tutorials/ruby/ruby-for-newbies-working-with-datamapper/我正在连接到数据库并这样迁移:DataMapper.setup:default,"sqlite://#{Dir.pwd}/ex2.db"DataMapper.auto_migrate!我的数据模型:classUserincludeDataMapper::Resourceproperty:id,Serialproperty:username,Stri

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