Change Box

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42个Rails Tips

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原文: From RailsConf 2012 - 10 Things You Didn’t Know Rails Could do

本文适用Rails 版本 3.2.3

Tip 1 : Run From A Single File 可以单文件运行

source

http://thesmallestrailsapp.com/ 
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%w(action_controller/railtie coderay).map &method(:require)

run TheSmallestRailsApp ||= Class.new(Rails::Application) {
  config.secret_token = routes.append { root to: 'hello#world' }.inspect
  initialize!
}

class HelloController < ActionController::Base
  def world
    render inline: "
      <!DOCTYPE html>
      <title>The Smallest Rails App</title>
      <h3>I am the smallest rails app!</h3>
      <p>Here is my source code:</p>
      #{CodeRay.scan_file(__FILE__, :ruby).div(line_numbers: :table)}
      <a href='https://github.com/artemave/thesmallestrailsapp.com'>Make me smaller</a>
    "
  end
end

Tip 2: Remind you of things 提醒功能，TODO list

users_controller.rb 
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   class UsersController < ApplicationController
     # TODO:  Make it possible to create new users.
   end
user.rb 
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  class User < ActiveRecord::Base
    # FIXME: Should token really  be accessible?
    attr_accessible :bil, :email, :name, :token
  end
index.html.erb 
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  <%# OPTIMIZE: Paginate this listing. %>
  <%= render Article.all %>

a. 执行命令:

$ rake notes

会输出如下结果：

app/controllers/users_controller.rb:
  * [ 2] [TODO] Make it possible to create new users.

app/models/user.rb:
  * [ 2] [FIXME] Should token really be accessible?

app/views/articles/index.html.erb:
  * [ 1] [OPTIMIZE] Paginate this listing.

b. 执行命令:

$ rake notes:todo

会只输出和TODO相关的：

app/controllers/users_controller.rb:
  * [ 2] Make it possible to create new users.

c. 执行命令:

$ rake notes:fixme

会只输出和FIXME相关的：

app/models/user.rb:
  * [ 2] Should token really be accessible?

d. 还可以自定义:

article.rb 
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  class Article < ActiveRecord::Base
    belongs_to :user
    attr_accessible :body, :subject
    # JEG2: Add that code from your blog here.
  end

执行命令：

$ rake notes:custom ANNOTATION=JEG2

会输出结果：

app/models/article.rb:
  * [ 4]Add that code from your blog here.

e. 在TextMate里面你还可以使用TODO 插件

Tip 3: Sandbox your Console 使用沙箱控制台

执行命令:

rails c --sandbox

使用这个控制台，里面任何的改变都会在你退出之后自动回滚到你未修改前的数据。

执行命令:

rails r 'p [Article, Comment, User].map(&:count)'

rails r 会执行引号里的代码。

Tip 4: Run Helper Methods in the Console 在控制台运行Helper方法

in the Console 
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   $ rails c
   Loading development environment (Rails 3.2.3)
   >> helper.number_to_currency(100)
   => "$100.00"
   >> helper.time_ago_in_words(3.days.ago)
   => "3 days"

Tip 5: Use Non-WEBrick Servers in Development 在开发中使用非Webrick服务器

Gemfile 
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   source "https://rubygems.org"
   # ...

   group :development do
     gem 'thin'
   end

执行命令：

% rails s thin

Tip 6: Allow you to tab into its configuration 自定义配置

lib/custom/railtie.rb 
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   module Custom
     class Railtie < Rails::Railtie
       config.custom = ActiveSupport::OrderedOptions.new
     end
   end
config/application.rb 
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   require_relative "../lib/custom/railtie"

   module Blog
     class Application < Rails::Application
       # ...
       config.custom.setting = 42
     end
   end

Tip 7: Keep you Entertained

RubyDramas

Tip 8: UnderStand Shorthand Migrations 理解便携的迁移文件

$ rails g resources user name:string email:string token:string bio:text

可以简写为：

$ rails g resources user name email token:string{6} bio:text

生成migrations:

Migrations 
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   class CreateUsers < ActiveRecord::Migration
     def change
       create_table :users do |t|
         t.string :name
         t.string :email
         t.string :token, :limit => 6
         t.text :bio
         t.timestamps
       end
     end
   end

Tip 9: Add Indexes to Migrations 增加索引

$rails g resource user name:index email:uniq token:string{6} bio:text

生成：

Migrations 
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   class CreateUsers < ActiveRecord::Migration
     def change
       create_table :users do |t|
         t.string :name
         t.string :email
         t.string :token, :limit => 6
         t.text :bio
         t.timestamps
       end
       add_index :users, :name
       add_index :users, :email, :unique => true
     end
   end

Tip 10: Add Associations to a Migration 增加关联关系到迁移文件

$rails g resource article user:references subject body:text

生成Migrations文件和model文件：

Migrations 
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   class CreateArticles < ActiveRecord::Migration
     def change
       create_table :articles do |t|
         t.references :user
         t.string :subject
         t.text :body
         t.timestamps
       end
       add_index :articles, :user_id
     end
   end
models/article.rb 
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   class Article < ActiveRecord::Base
     belongs_to :user
     attr_accessible :body, :subject
   end

还可以使用命令：

rails g resource comment user:blongs_to article:belongs_to body:text

会生成和user、article相关联的model和migration文件。

Tip 11: Show you the status of the database 显示数据库状态

使用命令：

 $ rake db:migrate:status

输出:

 database: db/development.sqlite3

 status   Migration ID    Migration Name
 ---------------------------------------
   up     20120414155612  Create users
   up     20120414160528  Create articles
  down    20120414161355  Create comments

Tip 12: Import your CSV Data

csv data:

Name,Email
James,james@example.com
Dana,dana@example.com
Summer,summer@example.com

导入代码：

import csv 
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   require 'csv'

   namespace :users do
     desc "Import users from a CSV file"
     task :import => :environment do
       path = ENV.fetch("CSV_FILE") {
         File.join(File.dirname(__FILE__), *%w[.. .. db data users.csv])
       }
       CSV.foreach(path, headers: true, header_converters: :symbol) do |row|
         User.create(row.to_hash)
       end
     end
   end

注意:

  • headers: true, header_converters: :symbol 这个配置项
  • row.to_hash

Tip 13 : Store CSV in Your Database 在数据库里存储CSV

store csv 
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  class Article <  ActiveRecord::Base
    require 'csv'
    module CSVSerializer
      module_function
      def load(field); field.to_s.parse_csv; end
      def dump(object); Array(object).to_csv; end
    end
    serialize :categories, CSVSerializer

    # ...

    attr_accessible :body, :subject, :categories
  end

Tip 14: “Pluck” Fields out of your database 从数据库‘Pluck’字段。

$ rails c
loading development environment(Rails 3.2.3)

>> User.select(:email).map(&:email)
  User Load(0.1ms) SELECT email FROM "users"
=> ["james@example.com", "dana@example.com", "summer@example.com"]
>> User.pluck(:email)
   (0.2ms) SELECT email FROM "users"
=> ["james@example.com", "dana@example.com", "summer@example.com"]
>> User.uniq.pluck(:email)
   (0.2ms) SELECT DISTINCT email FROM "users"
=> ["james@example.com", "dana@example.com", "summer@example.com"]

Tip 15: Count Records in Groups

$ rails g resource event article:belongs_to trigger

进控制台

$ rails c

>> article = Article.last
=> #<Article id:1, ...>
>> {edit:3, view:10}.each do |trigger, count|
?>   count.times do
?>     Event.new(trigger: trigger).tap{ |e| e.article= article; e.save! }
?>   end
=> {:edit => 3, :view => 10}
>> Event.count
=> 13
>> Event.group(:trigger).count
=> {"edit" => 3, "view" => 10}

Tip 16: Allow you to Override Associations

car.rb 
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  class Car < ActiveRecord::Base
    belongs_to :owner
    belongs_to :previous_owner, class_name: "Owner"

    def owner=(new_owner)
      self.previous_owner = owner
      super
    end
  end

Tip 17: Instantiate Records without a database

$ rails c

>> User.find(1)
=> #<User id: 1, name: "James", ...>
>> jeg2 = User.instantiate("id" => 1, "email" => "james@example.com")
=> #<User id:1, email:"james@example.com">
>> jeg2.name = "James Edward Gray II"
>>jeg2.save!
=> true

伪造一条记录。

TODO ….

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