我有两个模型在带有 Carrierwave 的 Rails 项目中使用相同的 uploader
class Brand < ActiveRecord::Base
mount :avatar, AvatarUploader
end
class Profile < ActiveRecord::Base
mount :avatar, AvatarUploader
end
然后当我尝试将一个图像复制到另一个模型时
profile.avatar = brand.avatar
profile.save!
失败并显示以下堆栈跟踪
undefined method `content_length' for nil:NilClass
usr/lib64/ruby/gems/1.9.1/gems/carrierwave-0.9.0/lib/carrierwave/storage/fog.rb:238:in `size'
/usr/lib64/ruby/gems/1.9.1/gems/carrierwave-0.9.0/lib/carrierwave/uploader/proxy.rb:57:in `size'
/usr/lib64/ruby/gems/1.9.1/gems/carrierwave-0.9.0/lib/carrierwave/sanitized_file.rb:95:in `size'
/usr/lib64/ruby/gems/1.9.1/gems/carrierwave-0.9.0/lib/carrierwave/sanitized_file.rb:135:in `empty?'
/usr/lib64/ruby/gems/1.9.1/gems/carrierwave-0.9.0/lib/carrierwave/uploader/cache.rb:119:in `cache!'
/usr/lib64/ruby/gems/1.9.1/gems/carrierwave-0.9.0/lib/carrierwave/mount.rb:327:in `cache'
/usr/lib64/ruby/gems/1.9.1/gems/carrierwave-0.9.0/lib/carrierwave/mount.rb:179:in `avatar='
/usr/lib64/ruby/gems/1.9.1/gems/carrierwave-0.9.0/lib/carrierwave/orm/activerecord.rb:38:in `avatar='
/usr/share/nginx/cranberrychic/releases/20140213171925/app/services/brand_into_user_converter.rb:42:in `copy_avatar'
/usr/share/nginx/cranberrychic/releases/20140213171925/app/services/brand_into_user_converter.rb:13:in `convert'
(irb):64:in `block (2 levels) in irb_binding'
/usr/lib64/ruby/gems/1.9.1/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction'
/usr/lib64/ruby/gems/1.9.1/gems/activerecord-3.2.13/lib/active_record/transactions.rb:208:in `transaction'
/usr/lib64/ruby/gems/1.9.1/gems/newrelic_rpm-3.6.0.78/lib/new_relic/agent/method_tracer.rb:486:in `block in transaction_with_trace_ActiveRecord_self_name_transaction'
/usr/lib64/ruby/gems/1.9.1/gems/newrelic_rpm-3.6.0.78/lib/new_relic/agent/method_tracer.rb:235:in `trace_execution_scoped'
/usr/lib64/ruby/gems/1.9.1/gems/newrelic_rpm-3.6.0.78/lib/new_relic/agent/method_tracer.rb:481:in `transaction_with_trace_ActiveRecord_self_name_transaction'
(irb):62:in `block in irb_binding'
/usr/lib64/ruby/gems/1.9.1/gems/activerecord-3.2.13/lib/active_record/relation/delegation.rb:6:in `each'
/usr/lib64/ruby/gems/1.9.1/gems/activerecord-3.2.13/lib/active_record/relation/delegation.rb:6:in `each'
(irb):59:in `irb_binding'
/usr/lib64/ruby/1.9.1/irb/workspace.rb:80:in `eval'
/usr/lib64/ruby/1.9.1/irb/workspace.rb:80:in `evaluate'
/usr/lib64/ruby/1.9.1/irb/context.rb:254:in `evaluate'
/usr/lib64/ruby/1.9.1/irb.rb:159:in `block (2 levels) in eval_input'
/usr/lib64/ruby/1.9.1/irb.rb:273:in `signal_status'
/usr/lib64/ruby/1.9.1/irb.rb:156:in `block in eval_input'
/usr/lib64/ruby/1.9.1/irb/ruby-lex.rb:243:in `block (2 levels) in each_top_level_statement'
/usr/lib64/ruby/1.9.1/irb/ruby-lex.rb:229:in `loop'
/usr/lib64/ruby/1.9.1/irb/ruby-lex.rb:229:in `block in each_top_level_statement'
/usr/lib64/ruby/1.9.1/irb/ruby-lex.rb:228:in `catch'
/usr/lib64/ruby/1.9.1/irb/ruby-lex.rb:228:in `each_top_level_statement'
/usr/lib64/ruby/1.9.1/irb.rb:155:in `eval_input'
/usr/lib64/ruby/1.9.1/irb.rb:70:in `block in start'
/usr/lib64/ruby/1.9.1/irb.rb:69:in `catch'
/usr/lib64/ruby/1.9.1/irb.rb:69:in `start'
/usr/lib64/ruby/gems/1.9.1/gems/railties-3.2.13/lib/rails/commands/console.rb:47:in `start'
/usr/lib64/ruby/gems/1.9.1/gems/railties-3.2.13/lib/rails/commands/console.rb:8:in `start'
/usr/lib64/ruby/gems/1.9.1/gems/railties-3.2.13/lib/rails/commands.rb:41:in `<top (required)>'
script/rails:6:in `require'
script/rails:6:in `<main>'
对我来说，这是带有雾存储的载波的一个错误，因为在文件存储的开发中，一切都按预期进行。当我尝试使用载波以任何可能的方式将图像从一个模型复制到另一个模型时，它会失败并出现相同的错误
我的Carrierwave版本是0.9.0
rails版本是3.2.13，ruby版本是1.9.3-p327
请您参考如下方法:
我相信你做错了
profile.avatar = brand.avatar
将不起作用，因为 profile.avatar= 需要一个 file 对象，而 brand.avatar 不会为您提供文件对象(它返回给您一个上传者，即头像对象)
我相信您正在寻找这种方法
profile.remote_avatar_url = brand.avatar.url
profile.save!
考虑到 brand.avatar.url 为您提供了一个可以下载该文件的 URL
有关remote_{uploader}_url的更多信息也可以在Carrierwave Readme中找到。
希望这有帮助