Ruby 命名错误：未定义的方法<&书信电报；零级：零级

我正在学习sinatra，我得到以下错误

Boot Error

Something went wrong while loading recall.rb
NoMethodError: undefined method `<<' for nil:NilClass

/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/rack-flash-0.1.2/lib/rack/flash.rb:11:in `use'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/bin/shotgun:128:in `block (2 levels) in <top (required)>'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:104:in `instance_eval'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:104:in `block in assemble_app'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.1/lib/rack/builder.rb:51:in `instance_eval'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.1/lib/rack/builder.rb:51:in `initialize'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:103:in `new'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:103:in `assemble_app'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:86:in `proceed_as_child'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:31:in `call!'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:18:in `call'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/favicon.rb:12:in `call'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/static.rb:14:in `call'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.1/lib/rack/builder.rb:134:in `call'
/Users/nikhil/.rvm/gems/ruby-1.9.3-p194/gems/rack-1.4.1/lib/rack/handler/webrick.rb:59:in `service'
/Users/nikhil/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
/Users/nikhil/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
/Users/nikhil/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'

---

您使用的是旧版本的rack flash，与您使用的rack版本不兼容。引发错误的线路在机架闪存内部，它试图改变一些机架内部状态，而这些状态后来发生了变化

---

出于某种原因，最新版本的gem被称为rack-flash3，这就是为什么安装rack-flash仍然可以获得gem的旧版本。

我已经安装了

rack-flash3

gem。我应该对源代码进行哪些更改？我应该改用

rack-flash3

吗？需要新的gem。不要认为您需要更改任何其他内容，因为我已将其修复。require语句保持不变。我建议改用

sinatra flash

。在gem文件中，执行

gem'rack-flash3'

，但仍然

require'rack flash'

。

require "sinatra"
require "data_mapper"
require "rack-flash"
require "sinatra/redirect_with_flash"