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在我的Rails3中发动机的Gemfile，我说：Rails3中发动机：宝石（回形针和inherited_resources）不加载
gem 'paperclip'
gem 'inherited_resources'
我也添加到了我的gemspec：
s.add_dependency "paperclip"
s.add_dependency "inherited_resources"
我然后跑捆绑安装为我的引擎和客户端应用程序，并启动了客户端应用程序的控制台，以便首先测试回形针，我得到：
Using /Users/ynkr/.rvm/gems/ruby-1.9.2-p180 with gemset rails31beta
ynkr % rails c
/Users/ynkr/.rvm/gems/[email protected]/gems/actionpack-3.1.0.rc4/lib/action_dispatch/http/mime_type.rb:101: warning: already initialized constant YML
Loading development environment (Rails 3.1.0.rc4)
ruby-1.9.2-p180 :001 > b=Blog::Blog.first
Blog::Blog Load (0.2ms) SELECT `blogs`.* FROM `blogs` LIMIT 1
=> #<Blog::Blog id: 1, user_id: 1, context_id: 2, title: "Cmd Line Blog Title", title_for_url: "cmd-line-blog-title", teaser: "This is the teaser for the command line blog", content: "Some content for the cmd line blog", created_at: "2011-06-28 06:06:55", updated_at: "2011-06-28 06:06:55">
ruby-1.9.2-p180 :002 > b.photos
NoMethodError: undefined method `has_attached_file' for #<Class:0x00000102a57fc8>
from /Users/ynkr/.rvm/gems/[email protected]/gems/activerecord-3.1.0.rc4/lib/active_record/base.rb:1078:in `method_missing'
from /websites/gems/blog/app/models/blog/photo.rb:6:in `<class:Photo>'
from /websites/gems/blog/app/models/blog/photo.rb:1:in `<top (required)>'
from /Users/ynkr/.rvm/gems/[email protected]/gems/activesupport-3.1.0.rc4/lib/active_support/dependencies.rb:452:in `load'
好吧，所以看起来无法找到来自paperclip gem的has_attached_file方法。为什么？我不确定。
移动到inherited_resources，我改变产生控制器支架，看起来像以下：
class Blog::ContextsController < InheritedResources::Base
before_filter :redirect_unless_admin
end
和加载索引页为实现这一目标，我很欢迎（在日志中）与：
Started GET "/blog/contexts" for 127.0.0.1 at 2011-06-28 12:06:25 -0700
ActionController::RoutingError (uninitialized constant InheritedResources):
Rendered /Users/ynkr/.rvm/gems/[email protected]/gems/actionpack-3.1.0.rc4/lib/action_dispatch/middleware/templates/rescues/routing_error.erb within rescues/layout (0.5ms)
我的问题是为什么这些不起作用？我的直觉是，有一些关于引擎，命名空间和加载宝石的东西，我完全没有意识到。