《Agile Web Development With Rails》Notebook.
环境：
Rails 3.1.0
Gem 1.8.10
Ruby ruby 1.9.2p180
1. rails depot
2. rails generate scaffold Product title:string description:text image_url:string price:decimal
报错：/1.9.1/gems/execjs-1.2.8/lib/execjs/runtimes.rb:47:in `autodetect': Could not find a JavaScript runtime. See
https://github.com/sstephenson/execjs for a list of available runtimes. (ExecJS::RuntimeUnavailable)
解决方法：
在Gemfile中增加：
gem 'execjs'
gem 'therubyracer'
然后运行：
bundle install
3. db/migrate/20110922081755_create_products.rb 是一个migration。migration代表a change we want to make to the data.
4. rake db:migrate
Rake looks for all the migrations not yet applied to the database and applies them.
报错：
uninitialized constant Rake::DSL
解决方法：
gem install rake
5. rails server -p 3002
6. 修改app/views/products/_form.html.erb
7. rake test