MongomapperとSinatraの未定義メソッド `update_attributes 'for nil：NilClass

Question

MongoMapperでSinatraを使用しているときにエラーが"未定義のメソッドupdate_attributes "をNil：NilClass"にしています。

モデル：私はエラーを取得し

class Publication 
include MongoMapper::Document 

key :page, String 
key :title, String 
key :body, String 
end 

とコード：

post '/edit' do 
@article = Publication.update({:page => 'main'}, {$set => {:title => params[:title], :body => params[:body]}}) 
end 

私はモンゴコンソールに更新を作ってみましたことだし、それが正常に更新されました：

> db.publications.update({page: 'main'},{$set: {body: '333', title: '111'}}) 
> db.publications.find({page: 'main'}) 
{ "_id" : ObjectId("4fa45046530a6978e3000003"), "body" : "333", "page" : "main", "title" : "111" } 

全スタックトレース：

[2012-05-06 03:04:22] INFO WEBrick 1.3.1 
[2012-05-06 03:04:22] INFO ruby 1.8.7 (2010-01-10) [universal-darwin11.0] 
== Sinatra/1.3.2 has taken the stage on 4567 for development with backup from WEBrick 
[2012-05-06 03:04:23] INFO WEBrick::HTTPServer#start: pid=32266 port=4567 
localhost - - [06/May/2012:03:04:27 MSK] "GET /edit HTTP/1.1" 200 193 
- -> /edit 
localhost - - [06/May/2012:03:04:27 MSK] "GET /favicon.ico HTTP/1.1" 404 447 
- -> /favicon.ico 
NoMethodError - undefined method `update_attributes' for nil:NilClass: 
/Library/Ruby/Gems/1.8/gems/mongo_mapper- 0.11.1/lib/mongo_mapper/plugins/querying.rb:118:in `update_single' 
/Library/Ruby/Gems/1.8/gems/mongo_mapper-0.11.1/lib/mongo_mapper/plugins/querying.rb:117:in `tap' 
/Library/Ruby/Gems/1.8/gems/mongo_mapper-0.11.1/lib/mongo_mapper/plugins/querying.rb:117:in `update_single' 
/Library/Ruby/Gems/1.8/gems/mongo_mapper-0.11.1/lib/mongo_mapper/plugins/querying.rb:45:in `update' 
main.rb:48:in `POST /edit' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:1211:in `call' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:1211:in `compile!' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:785:in `[]' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:785:in `route!' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:801:in `route_eval' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:785:in `route!' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:822:in `process_route' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:820:in `catch' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:820:in `process_route' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:784:in `route!' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:783:in `each' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:783:in `route!' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:886:in `dispatch!' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:719:in `call!' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:871:in `invoke' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:871:in `catch' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:871:in `invoke' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:719:in `call!' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:705:in `call' 
/Library/Ruby/Gems/1.8/gems/rack-protection-1.2.0/lib/rack/protection/xss_header.rb:22:in `call' 
/Library/Ruby/Gems/1.8/gems/rack-protection-1.2.0/lib/rack/protection/path_traversal.rb:16:in `call' 
/Library/Ruby/Gems/1.8/gems/rack-protection-1.2.0/lib/rack/protection/json_csrf.rb:17:in `call' 
/Library/Ruby/Gems/1.8/gems/rack-protection-1.2.0/lib/rack/protection/base.rb:47:in `call' 
/Library/Ruby/Gems/1.8/gems/rack-protection-1.2.0/lib/rack/protection/xss_header.rb:22:in `call' 
/Library/Ruby/Gems/1.8/gems/rack-1.4.1/lib/rack/logger.rb:15:in `call' 
/Library/Ruby/Gems/1.8/gems/rack-1.4.1/lib/rack/head.rb:9:in `call' 
/Library/Ruby/Gems/1.8/gems/rack-1.4.1/lib/rack/methodoverride.rb:21:in `call' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/showexceptions.rb:21:in `call' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:1334:in `call' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:1416:in `synchronize' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:1334:in `call' 
/Library/Ruby/Gems/1.8/gems/rack-1.4.1/lib/rack/handler/webrick.rb:59:in `service' 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/httpserver.rb:104:in `service' 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/httpserver.rb:65:in `run' 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:173:in `start_thread' 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:162:in `start' 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:162:in `start_thread' 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:95:in `start' 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:92:in `each' 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:92:in `start' 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:23:in `start' 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:82:in `start' 
/Library/Ruby/Gems/1.8/gems/rack-1.4.1/lib/rack/handler/webrick.rb:13:in `run' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/base.rb:1295:in `run!' 
/Library/Ruby/Gems/1.8/gems/sinatra-1.3.2/lib/sinatra/main.rb:25 
main.rb:53 

誰もが私は適切にRubyコードに更新されませんどのような理由のために言うことができますか？

Answer 1

あなたはおそらく、あなたのキーとして:$setの代わり$setを持っている意味：

@article = Publication.update({:page => 'main'}, {:$set => {:title => params[:title], :body => params[:body]}}) 

あなたは（nilへのすべてのグローバル変数のデフォルト以降）nilをあるキーのグローバル変数$setを使用しているが何をしています。例：

{ $set => "something" } #=> {nil=>"something"} 
{ :$set => "something" } #=> {:$set=>"something"}