mac系统中搭建rails3+MongoDB的demo工程

环境： ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-darwin11.4.0]

rvm 1.14.5 (stable) by Wayne E. Seguin , Michal Papis [https://rvm.io/]
Rails 3.2.6 MongoDB?db version v2.0.6, pdfile version 4.5

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终端中执行命令：

rails new mongodemo gem install mongo_mapper

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在enviroment.rb中添加config.gem "mongo_mapper" 如启动报config变量无法找到，则修改config.gem "mongo_mapper"为$config.gem "mongo_mapper"
异常信息： /Users/seraph/Documents/rails_projects/mongodemo/config/environment.rb:7:in `': undefined local variable or method `config' for main:Object (NameError)
$config代表全局变量引用

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在config/initalizers中添加文件mongo_config.rb
内容：MongoMapper.database = "mongodemo-#{Rails.env}"

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在Gemfile中添加 source "http://gemcutter.org"
gem 'mongo_mapper', github: "jnunemaker/mongomapper" gem "bson_ext" gem "nifty-generators", :group => :development 然后执行命令：bundle install
使用脚手架，生成MongoDB演示代码： rails generate scaffold project name:string --orm=mongo_mapper rails generate scaffold task project_id:string name:string completed:boolean --orm=mongo_mapper

访问MongoDB:?http://localhost:28017/

各种异常情况处理：

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1.问题：启动Rails服务器如报如下异常，说明没有安装bson_ext.
? gem install bson_ext
? If you continue to receive this message after installing, make sure that the ? bson_ext gem is in your load path and that the bson_ext and mongo gems are of the same version.

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2.问题：在使用nifty生成代码时，如报如下异常，需执行：gem install nifty-generators rails g nifty:scaffold Recipe name:string index new
/Users/seraph/.rvm/gems/ruby-1.9.3-p194@global/gems/bundler-1.1.4/lib/bundler/resolver.rb:287:in `resolve': Could not find gem 'nifty-generators (>= 0) ruby' in the gems available on this machine. (Bundler::GemNotFound)

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3.问题：mongodb演示，访问http://localhost:3000/projects时，报异常：undefined method `key?' for nil:NilClass 解决： （1）在Gemfile中添加 （2）在终端中运行?bundle install 解释： Explanation: Rails 3.2.4 added a accessible_attributes method to ActiveModel, but MongoMapper already had this; so they were clobbering each other. 链接：http://stackoverflow.com/questions/11000788/undefined-method-key-for-nilnilclass-when-using-mongomapper

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4.问题：访问http://localhost:3000/projects时，报如下异常：
ArgumentError (wrong number of arguments (1 for 0)): ? app/controllers/projects_controller.rb:1:in `'
解决办法：未能明确，怀疑

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5.问题：如果访问MongoDBhttp://localhost:28017/页面时，页面提示需开启rest，则在/usr/local/mongodb/mongod.conf文件中添加 rest = true 全部内容是： # Store data alongside MongoDB instead of the default, /data/db/ dbpath = /usr/local/mongodb_data
# Only accept local connections bind_ip = 127.0.0.1
# Seraph add, to enable REST rest = true