从Rails2到Rails3

我们来看下rails3相比rails2, 进步在哪里, 优势又在什么地方.

 

1. 脚本命令

旧的命令                                      新的用法

script/generate                          rails g

script/console                            rails c

script/server                              rails s

script/dbconsole                        rails db

 

2. 配置文件

rails2: config/environment.rb

Rails::Initializer.run do |config|
    config.load_paths += % W ( #{RAILS_ROOT}/extras )
    config.gem "bj"
    config.gem "sqlite3-ruby" , :lib => "sqlite3"
    config.gem "aws-s3" , :lib => "aws/s3"
   config.plugins = [ :exception_notification ]
   config.time_zone = 'UTC'
end

rails3:config/application.rb

module APP_NAME
    class Application < Rails::Application
        config.load_paths += % W ( #{RAILS_ROOT}/extras )
        config.plugins = [ :exception_notification ]
        config.time_zone = 'UTC'
    end
end

这样就变成了一种架构式的应用, 我们可以根据方便的对config进行操作

 

3. 路由

在rails3中, 已经的路由可以继续工作, 而新的路由方式更加简洁.

在 rails2 中:

map.resources :posts do |post|
    post.resources :comments
end

而在rails3中, 表达更为形象:
 

resources :posts do
    resources :comments
end

对于一些复杂的路由, rails2:

post.resources :comments ,
                 :member => { :preview => :post },
                :collection => { :archived => :get }

 在rails3中可以这样表达:

resources :comments do
    member do
        post :preview
    end
    collection do
        get :archived
    end
end

不够简洁? 我们还可以这样做:

resources :comments do
    post :preview , :on => :member
    get :archived , :on => :collection
end

对于基本路由, rails2:

map.connect 'login' , :controller => 'session' , :action => 'new'

 那么在rails3中:

match 'login' => 'session#new'

对于具名路由, rails2:

map.login 'login' , :controller => 'session' , :action => 'new'

在rails3中:

match 'login' => 'session#new' , :as => :login

对于程序根路由, rails2:

map.root :controller => 'users' , :action => 'index'

rails3:

root :to => 'users#index'

对于遗留路由, rails2:

map.connect ':controller/:action/:id'
map.connect ':controller/:action/:id.:format'

 那么在rails3中写法更优雅:

match ':controller(/:action(/:id(.:format)))'

对于路由参数, rals2:

map.connect '/articles/:year/:month/:day' , :controller => 'posts' , :action => 'index'

rails3:
 

match '/articles/:year/:month/:day' => "posts#index"

那么对于存档请求, 比如rails2:

map.connect '/articles/:year/:month/:day' , :controller => 'posts' , :action => 'index'
map.connect '/articles/:year/:month' , :controller => 'posts' , :action => 'index'
map.connect '/articles/:year' , :controller => 'posts' , :action => 'index'

在rails3中:
 

match '/articles(/:year(/:month(/:day)))' => "posts#index"

指定请求方式, rails2:

map.connect '/articles/:year' , :controller => 'posts' , :action => 'index' ,
:conditions => { :method => :get }

在rails3中:
 

match '/articles/:year' => "posts#index" , :via => :get
#或者更简单的:
get '/articles/:year' => "posts#index"

对于跳转, rails3:

match 'signin' , :to => redirect( "/login" )
match 'users/:name' , :to => redirect {|params| "/#{params[:name]}" }
match 'google' => redirect( 'http://www.google.com/' )

路由约束: rails2中实际上使用了 :requirements 符号

map.connect '/:year' , :controller => 'posts' , :action => 'index' ,
                                    :requirements => { :year => /\d{ 4 }/ }

在rails3中:
 

match '/:year' => "posts#index" , :constraints => { :year => /\d{ 4 }/}

:constraints => { :user_agent => /iphone/ }
:constraints => { :ip => / 192 \. 168 \. 1 \.\d{ 1 , 3 }/ }
constraints( :host => /localhost/) do
    resources :posts
end
constraints IpRestrictor do
   get 'admin/accounts' => "queenbee#accounts"
end

对于Rack应用, rails3:

get 'hello' => proc { |env| [ 200 , {}, "Hello Rack" ] }
get 'rack_endpoint' => PostsController.action( :index )
get 'rack_app' => CustomRackApp

4. Bundler与ActionController

一个典型的rails应用, 我们一般需要在 environment.rb 指定你的 gems:

config.gem "haml"
config.gem "chronic" , :version => '0.2.3'

然后我们运行 $ rake gems:install, 该命令会取得并下载然后安装编译这些gems到你的系统RubyGems目录中.

之后我们运行 $ rake gems:unpack:dependencise, 把这些gem打包到你应用程序的vendor/gems目录中去.

 

这样做产生的问题:

1. 它直接绑定到Rails中

2. 没有从本质上解决依赖问题

3. 运行时容易发生冲突

 

在rails3中, 使用了 bundle 命令:

直接在你的 gemfile 中指定你的 gem

gem "haml"
gem "chronic" , '0.2.3'

然后运行 $ bundle, 该命令会会取得并下载然后安装编译这些gems

然后运行 $ bundle package 把gem源移到/vendor/cache中去.

这样rails应用中的gem与系统中的gem就不会相冲突.

一般的控制器语法:

class UsersController < ApplicationController
    def index
       @users = User.all
        respond_to do |format|
            format.html
            format.xml { render :xml => @users .to_xml }
        end
    end

    def show
       @user = User.find(params[ :id ])
        respond_to do |format|
            format.html # show.html.erb
            format.xml { render :xml => @user }
        end
    end

....

改进的语法:

class UsersController < ApplicationController
    respond_to :html , :xml , :json
    def index
        @users = User.all
       respond_with( @users )
    end
   def show
       @user = User.find(params[ :id ])
        respond_with( @user )
    end
....

5. ActionMailer

rails2:  $ script/generate mailer UserMailer welcome forgot_password

这将创建 app/models/user_mailer.rb

那么在rails3中: $ rails g mailer UserMailer welcome forgot_password

这将创建 app/mailers/user_mailer.rb

 

在实现部分, rails2:

def welcome(user, subdomain)
    subject 'Welcome to TestApp'
   recipients user.email
    from '[email protected]'
    body :user => user, :subdomain => subdomain
end

UserMailer.deliver_welcome(user, subdomain)

在rails3中:

def welcome(user, subdomain)
    @user = user
    @subdomain = subdomain
    mail( :from => "[email protected]" ,
            :to => user.email,
           :subject => "Welcome to TestApp" )
end

UserMailer.welcome(user, subdomain).deliver

相比rails2, 我们在rails3下实现一个mail要简单的多:

class UserMailer < ActionMailer::Base
    default :from => "[email protected]" ,
                :reply_to => "[email protected]" ,
               "X-Time-Code" => Time .now.to_i.to_s
    def welcome(user, subdomain)
        @user = user
        @subdomain = subdomain
        attachments[ 'test.pdf' ] = File .read( "#{Rails.root}/public/test.pdf" )
        mail( :to => @user .email, :subject => "Welcome to TestApp" ) do |format|
            format.html { render 'other_html_welcome' }
            format.text { render 'other_text_welcome' }
        end
    end
end

6. ActiveRelation 以及 ActiveModel

在rails2中, 我们经常使用下面的方法来进行查询:

@posts = Post.find( :all , :conditions => { :published => true })

该方式将立即查询数据库然后返回Posts数组

 

而在rails3中:

@posts = Post.where( :published => true )

该方法不会查询数据库, 仅仅返回一个 ActiveRecord::Relation 对象, 然后:
 

@posts = Post.where( :published => true )
if params[ :order ]
   @posts = @posts .order(params[ :order ])
end
@posts . each do |p|
    ...                 #在这里进行查询, 实现延迟加载
end

对于命名范围, 在rails2中:

class Post < ActiveRecord::Base
    default_scope :order => 'title'
    named_scope :published , :conditions => { :published => true }
    named_scope :unpublished , :conditions => { :published => false }
end

而在rails3中:

class Post < ActiveRecord::Base
    default_scope order( 'title' )
    scope :published , where( :published => true )
    scope :unpublished , where( :published => false )
end

对于查找方法, rails2:
 

Post.find( :all , :conditions => { :author => "Joe" }, :includes => :comments , :order => "title" , :limit => 10 )

在rails3:

Post.find( :all , :conditions => { :author => "Joe" }, :includes => :comments ,
:order => "title" , :limit => 10 )

7. 跨站点脚本(XSS)

在rails2中, 一般我们输入一段文本的时候, 我们往往会这样写: <%= h @post.body %>

那么在rails3中, <%= @post.body %> 默认输出的是一段safe html, 如果想输出XSS, 可以在前面加上 raw