Annotate models

   Rails的约定优于配置和Ruby的动态性，使得model类变得十分简洁，但是也带来了一个问题：如果你想知道一个model有哪些属性时，必须去查看数据库或者migration，这给开发带来了极大的不便。Annotate models插件很好地解决了这个问题，它在model类的起始处以注释的形式写明了所有的属性，下面来看个例子：
1. 创建工程：

$rails test_annotate_models
$cd rails test_annotate_models

2. 安装插件：

$script/plugin install http://repo.pragprog.com/svn/Public/plugins/annotate_models

3. 生成测试模型：

$script/generate model post title:string body:text
$rake db:migrate

4. 生成annotation：

$rake annotate_models

5. 效果：

引用

              # == Schema Information
              # Schema version: 1
              #
              # Table name: posts
              #
              #  id         :integer         not null, primary key
              #  title      :string(255)  
              #  body       :text         
              #  created_at :datetime     
              #  updated_at :datetime     
              #
             
              class Post < ActiveRecord::Base
              end

6. 增加模型：

$script/generate model comment body:text post:references
$script/generate migration add_comment_count_to_post

引用

              #db/migrate/003_add_comment_count_to_post.rb
              class AddCommentCountToPost < ActiveRecord::Migration
                def self.up
                  add_column :posts, :comment_count, :integer
                end
             
                def self.down
                  remove_column :posts, :comment_count
                end
              end

$rake db:migrate

7. 再试试annotation：

$rake annotate_models

引用

             # == Schema Information
              # Schema version: 3
              #
              # Table name: posts
              #
              #  id            :integer         not null, primary key
              #  title         :string(255)  
              #  body          :text         
              #  created_at    :datetime     
              #  updated_at    :datetime     
              #  comment_count :integer      
              #
             
              class Post < ActiveRecord::Base
              end
             
              # == Schema Information
              # Schema version: 3
              #
              # Table name: comments
              #
              #  id         :integer         not null, primary key
              #  body       :text           
              #  post_id    :integer        
              #  created_at :datetime       
              #  updated_at :datetime       
              #
             
              class Comment < ActiveRecord::Base
              end