我使用Ruby 1.9.3和Rails 3.0.11。我最近安装了Draper(0.12.0) gem，但我无法运行它的生成器。当我尝试在Post模型上运行生成器时，我得到以下错误:-
rails generate decorator Post
/home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.0.11/lib/active_support/whiny_nil.rb:48:in `method_missing': undefined method `config' for nil:NilClass (NoMethodError)
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/draper-0.12.0/lib/draper/railtie.rb:6:in `block in <class:Railtie>'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/railtie.rb:189:in `call'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/railtie.rb:189:in `each'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/railtie.rb:189:in `load_generators'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/application.rb:147:in `block in load_generators'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/application/railties.rb:11:in `each'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/application/railties.rb:11:in `all'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/application.rb:147:in `load_generators'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/generators.rb:319:in `load_generators_from_railties!'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/generators.rb:278:in `lookup'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/generators.rb:141:in `find_by_namespace'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/generators.rb:161:in `invoke'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/commands/generate.rb:10:in `<top (required)>'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:239:in `require'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:239:in `block in require'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:225:in `block in load_dependency'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:593:in `new_constants_in'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:225:in `load_dependency'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:239:in `require'
from /home/mohnish/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.0.11/lib/rails/commands.rb:17:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
任何输入，我如何调试这将是非常有帮助的。
谢谢。
问题出在v0.12.0(您正在使用的版本)https://github.com/drapergem/draper/blob/v0.12.0/lib/draper/railtie.rb#L5-L8
当我查看主分支时，它们变成了如下代码:https://github.com/drapergem/draper/blob/master/lib/draper/railtie.rb#L5-L10
你应该升级你的draper gem到最新版本，看看错误是否仍然发生。