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使用MySQL+DataMapper为Ruby Web应用增加数据库存储

在之前搭建的简单Ruby Web应用基础上增加数据库存储： ###工具集：

###步骤：

  1. 引入data_mapper、dm-mysql-adapter、dm-migrations、haml等gem，并bundle install安装：

     # Gemfile
 source 'http://ruby.taobao.org/'
 gem 'sinatra'
 gem 'unicorn'
 gem 'capistrano', '~> 2.15.5'
 gem 'rvm-capistrano'
 gem 'data_mapper'
 gem 'dm-mysql-adapter'
 gem 'dm-migrations'
 gem 'haml'

  2. 新增模型类。假设要增加一个简单的功能，用户在页面上通过表单输入一个字符串作为关键字，每提交一次，应用就将该关键字记录下来存储到数据库中，模型类如下：

     # models/history.rb
 class History
   include DataMapper::Resource

   property :id,               Serial
   property :keyword,          String
   property :created_at,       DateTime, :default => lambda { |r,p| Time.now }

 end  增加一段连接MySQL以及建立对象-关系映射的初始化代码，注意：  * `DataMapper.finalize`要在所有的模型类都已被引入之后调用  * `DataMapper.auto_upgrade!`执行时会自动根据模型类对数据库进行migration升级操作，与`DataMapper.auto_migrate!`方法不同的是，`auto_upgrade!`仅会更新数据库表结构而不抹除已有数据，`auto_migrate!`则会调整表结构并抹除已有数据。  ***

 # models/init.rb
 require 'data_mapper'
 require 'dm-migrations'
 require_relative 'history'

 # A MySQL connection:
 DataMapper.setup(:default, 'mysql://root@localhost/test') # Your mysql username and database
 DataMapper.finalize
 DataMapper.auto_upgrade!  并在app.rb中引入models/init.rb文件：

 # app.rb
 require 'sinatra'

 class App < Sinatra::Base
   get '/' do
     'Hello world'
   end
 end

 require_relative 'models/init'

  3. 新增模板文件。这里使用一个haml文件，包括一个简单的表单和提交按钮，供用户提交关键字。模板文件如下：

     # views/search.haml
 !!!
 %html
   %head
   %body
     %h3 Search
     %form.form{:action => '#', :method => 'get'}
       %fieldset
         %legend Keyword Input
         %ul
           %li
             %input#keyword{:type => 'text', :name => 'q', :value => params[:q]}
           %li
             %input{:type => 'submit', :value => 'Search'}

  4. 新增一个routes文件，用于响应表单提交请求：

     # routes/search.rb
 class App < Sinatra::Base

   get '/search' do
     q = params[:q]
     History.create(:keyword => q) unless q.nil? or q.strip.empty?
     haml :search
   end

 end  ***
 # routes/init.rb
 require_relative 'search'  另外`app.rb`中需`require_relative 'routes/init'`增加对routes文件的引入。

  5. push代码到git仓库后使用cap deploy进行部署。在正式部署之前需先在远程主机上安装mysql，部署时如果有类似于以下的报错：

       servers: ["115.28.137.21"]
   [root@115.28.137.21] executing command
 		** [out :: root@115.28.137.21] Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
 ** [out :: root@115.28.137.21] 
 ** [out :: root@115.28.137.21] checking for main() in -lmysqlclient... no
 ......
 ** [out :: root@115.28.137.21] make failed, exit code 2
 ** [out :: root@115.28.137.21] 
 ** [out :: root@115.28.137.21] Gem files will remain installed in /srv/dev-helper/shared/bundle/ruby/1.9.1/gems/do_mysql-0.10.13 for inspection.
 ** [out :: root@115.28.137.21] Results logged to /srv/dev-helper/shared/bundle/ruby/1.9.1/extensions/x86_64-linux/1.9.1/do_mysql-0.10.13/gem_make.out
 ** [out :: root@115.28.137.21] An error occurred while installing do_mysql (0.10.13), and Bundler cannot
 ** [out :: root@115.28.137.21] continue.
 ** [out :: root@115.28.137.21] Make sure that `gem install do_mysql -v '0.10.13'` succeeds before bundling.  多是因为找不到mysql安装路径所致，可以在远程主机上运行：
	
 bundle config build.do_mysql --with-mysql-config=/usr/bin/mysql  然后再进行部署。部署成功后就可以看到新功能生效了。

###参考：

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Published

07 February 2014

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