背景：我正在使用 Padrino、Ruby 1.9.2、HAML 和 Heroku 构建一个简单的博客。我希望帖子索引具有杂志般的外观。对于索引中的每个帖子，用户应该看到标题、内容预告和图像。我的问题是附加图像。
问题：我一直在尝试使用 Paperclip gem 将图像附加到每个帖子。Heroku 将从 Amazon S3 bin 中获取实际图像。到目前为止，当我尝试运行迁移时，出现错误：
$ .../base.rb:1088:in `method_missing': undefined method
`has_attached_file' for #<Class:0xa672140> (NoMethodError)
看起来 Paperclip 只是无法加载，但这是我卡住的地方。
详细信息：--Q：当我“尝试运行迁移”时我在做什么？--A：我将以下内容放入迁移文件夹
class AddPictureToPost < ActiveRecord::Migration
def self.up
change_table :posts do |t|
t.has_attached_file :picture
end
end
def self.down
drop_attached_file :posts, :picture
end
end
然后运行“padrino rake ar:migrate”
--Q：我在 Gemfile 中列出了回形针吗？——答：是的。
--Q：post模型是什么样的？ - 一个：
class Post < ActiveRecord::Base
has_attached_file :picture,
:storage => :s3,
:bucket => 'blog_images',
:s3_credentials => {
:access_key_id => ENV['S3_KEY'],
:secret_access_key => ENV['S3_SECRET']
}
end
--Q：app.rb 是什么样子的？ - 一个：
class Blog < Padrino::Application
register Padrino::Rendering
register Padrino::Mailer
register Padrino::Helpers
enable :sessions
get '/' do
haml :index
end
end
--Q：boot.rb 是什么样的？ - 一个：
PADRINO_ENV = ENV["PADRINO_ENV"] ||= ENV["RACK_ENV"] ||=
"development" unless defined?(PADRINO_ENV)
PADRINO_ROOT = File.expand_path('../..', __FILE__) unless defined?
(PADRINO_ROOT)
require 'rubygems' unless defined?(Gem)
require 'bundler/setup'
Bundler.require(:default, PADRINO_ENV)
Padrino.before_load do
end
Padrino.after_load do
end
Padrino.load!
--Q：完整的错误输出是什么样的？ - 一个：
jared:~/blog$ padrino rake ar:migrate
=> Executing Rake ar:migrate ...
/usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.1.3/lib/
active_record/base.rb:1088:in `method_missing': undefined method
`has_attached_file' for #<Class:0xa1ffb30> (NoMethodError)
from /home/jared/isthmus2/app/models/post.rb:2:in `<class:Post>'
from /home/jared/isthmus2/app/models/post.rb:1:in `<top (required)>'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:240:in `require'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:240:in `block in require'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:223:in `block in load_dependency'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:640:in `new_constants_in'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:223:in `load_dependency'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:240:in `require'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/reloader.rb:148:in `safe_load'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:162:in `block in require_dependencies'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:160:in `each'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:160:in `require_dependencies'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/application.rb:34:in `inherited'
from /home/jared/blog/app/app.rb:1:in `<top (required)>'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:240:in `require'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:240:in `block in require'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:223:in `block in load_dependency'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:640:in `new_constants_in'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:223:in `load_dependency'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:240:in `require'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/reloader.rb:148:in `safe_load'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:162:in `block in require_dependencies'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:160:in `each'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:160:in `require_dependencies'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/mounter.rb:148:in `locate_app_object'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/mounter.rb:30:in `initialize'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/mounter.rb:221:in `new'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/mounter.rb:221:in `mount'
from /home/jared/blog/config/apps.rb:34:in `<top (required)>'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:240:in `require'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:240:in `block in require'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:223:in `block in load_dependency'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:640:in `new_constants_in'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:223:in `load_dependency'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.1.3/lib/
active_support/dependencies.rb:240:in `require'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/reloader.rb:148:in `safe_load'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:162:in `block in require_dependencies'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:160:in `each'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:160:in `require_dependencies'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:70:in `block in load!'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:70:in `each'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/loader.rb:70:in `load!'
from /home/jared/blog/config/boot.rb:29:in `<top (required)>'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/cli/base.rb:56:in `require'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/cli/base.rb:56:in `block in rake'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/cli/base.rb:140:in `capture'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/lib/
padrino-core/cli/base.rb:56:in `rake'
from /usr/local/lib/ruby/gems/1.9.1/gems/thor-0.14.6/lib/thor/task.rb:
22:in `run'
from /usr/local/lib/ruby/gems/1.9.1/gems/thor-0.14.6/lib/thor/
invocation.rb:118:in `invoke_task'
from /usr/local/lib/ruby/gems/1.9.1/gems/thor-0.14.6/lib/thor.rb:
263:in `dispatch'
from /usr/local/lib/ruby/gems/1.9.1/gems/thor-0.14.6/lib/thor/base.rb:
389:in `start'
from /usr/local/lib/ruby/gems/1.9.1/gems/padrino-core-0.10.5/bin/
padrino:9:in `<top (required)>'
from /usr/local/bin/padrino:19:in `load'
from /usr/local/bin/padrino:19:in `<main>'
如果你已经读到这里……谢谢！我希望你能帮助我阐明这一点。