Tag ruby, everything about ruby | {:web=>:wxianfeng}

北京 798 Ruby/Rails 活动

Posted by wxianfeng Sat, 30 Jul 2011 06:36:00 GMT

时间: 2011-07-24
收获:
发现北京ROR的公司不是一般的多,签到单上看到N多公司,技术上没有太大收获,都是介绍性的,没有实战性的,内容主要涉及: mirah , Mongodb,Erlang,Grape

进程:http://www.surveymonkey.com/s/MSY2L7T

PS : 798 很好玩,很有艺术特色

现场:

798 入口

Ruby活动地方

Rails rumble 创始人

现场job board

现场

清一色老外,清一色Mac

介绍Mirah

798

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shell 文件插入行

Posted by wxianfeng Mon, 11 Jul 2011 10:44:00 GMT

一个rails2.x 的项目，需要迁移到rails3.x , ruby 1.9.2的编码问题,需要在rb文件头添加指定编码, 常见指定方式如下:

#coding:utf-8
#encoding:utf-8
# -*- coding: utf-8 -*-
# -*- encoding: utf-8 -*-

那么多rb文件总不能一个一个加吧,写个shell解决之!!!

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ruby rake tips

Posted by wxianfeng Wed, 26 Jan 2011 06:59:00 GMT

环境:ruby 1.9.2 + rake 0.8.7 + rails 3.0.3

今天在写 rake 文件，提示我没找到 model Class，问题在于我没加 => :environment , 那为什么加上 => :environment 就可以了 , 研究了下rake:

task :test => :environment do 
end

其中后面的 :environment 也是一个 task ，也就是说在执行 test 这个 task 之前会执行 :environment 这个 task，有点像rails controller 中的 before_filter ,那么 :environment 这个task 定义在什么地方，rails project中也没有啊。。。，定义在 rails 源码中了，你在你的project下执行 rake environment 不会报错的

wxianfeng@ubuntu:/usr/local/system/projects/entos/ent_os$ rake environment --trace 
(in /usr/local/system/projects/entos/ent_os)
** Invoke environment (first_time)
** Execute environment

不过也看不到输出什么信息，因为只是加载了运行环境而已 ,那么从哪里执行的，定义在 project 下 Rakefile 中了

# Add your own tasks in files placed in lib/tasks ending in .rake,
# for example lib/tasks/capistrano.rake, and they will automatically be available to Rake.

require File.expand_path('../config/application', __FILE__)
require 'rake'

EntOs::Application.load_tasks

继续跟踪 load_tasks:

最后找到了 task environment

   def initialize_tasks

      require "rails/tasks"

      task :environment do

        $rails_rake_task = true

        require_environment!

      end

    end

全部文件 here

所以加载了 environment 也就可以找到 model Class 了

总结:

1,rake 命名格式

rakefile, Rakefile, rakefile.rb, Rakefile.rb 都可以，常用 Rakefile

另外 rails 中使用的话，还可以使用 .rake 后缀的文件

2,设置命名空间

namespace :test do
end

3,设置默认task

task :default => ["test"]

可以指定多个 task,执行 rake 后，默认调用的是 default task

4，指定task执行顺序

task :test => [:hello,:world]

5,查看rake 任务

rake -T  
rake --tasks
rake -T db: # 查看db打头的task

6,跟踪task

rake test --trace

更多 options

wxianfeng@ubuntu:/usr/local/system/projects/entos/ent_os$ rake -h
rake [-f rakefile] {options} targets...

Options are ...
    -C, --classic-namespace          Put Task and FileTask in the top level namespace
    -D, --describe [PATTERN]         Describe the tasks (matching optional PATTERN), then exit.
    -n, --dry-run                    Do a dry run without executing actions.
    -e, --execute CODE               Execute some Ruby code and exit.
    -p, --execute-print CODE         Execute some Ruby code, print the result, then exit.
    -E, --execute-continue CODE      Execute some Ruby code, then continue with normal task processing.
    -I, --libdir LIBDIR              Include LIBDIR in the search path for required modules.
    -P, --prereqs                    Display the tasks and dependencies, then exit.
    -q, --quiet                      Do not log messages to standard output.
    -f, --rakefile [FILE]            Use FILE as the rakefile.
    -R, --rakelibdir RAKELIBDIR,     Auto-import any .rake files in RAKELIBDIR. (default is 'rakelib')
        --rakelib
    -r, --require MODULE             Require MODULE before executing rakefile.
        --rules                      Trace the rules resolution.
    -N, --no-search, --nosearch      Do not search parent directories for the Rakefile.
    -s, --silent                     Like --quiet, but also suppresses the 'in directory' announcement.
    -g, --system                     Using system wide (global) rakefiles (usually '~/.rake/*.rake').
    -G, --no-system, --nosystem      Use standard project Rakefile search paths, ignore system wide rakefiles.
    -T, --tasks [PATTERN]            Display the tasks (matching optional PATTERN) with descriptions, then exit.
    -t, --trace                      Turn on invoke/execute tracing, enable full backtrace.
    -v, --verbose                    Log message to standard output.
    -V, --version                    Display the program version.
    -h, -H, --help                   Display this help message.

DEMO:

wxianfeng@ubuntu:~/test/rake$ cat Rakefile 
desc "Default: test"
task :default => ["r:test"]

namespace :r do 
desc "test" 
task :test  do
        puts "test"
end

desc "test1"
task :test1 => :test do
        puts "test1" 
end

desc "test3"
task :test3 => :test4 do
        puts "test3" 
end 
end

SEE:

http://hi.baidu.com/%D0%C7203/blog/item/ebda2dd09f1d698ea1ec9c7a.html
http://guides.rubyonrails.org/command_line.html
http://ericzouthoughts.wordpress.com/2009/06/20/execute-shell-command-in-ruby-rake-task/

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ruby string to class

Posted by wxianfeng Thu, 17 Nov 2011 09:53:00 GMT

环境:ruby 1.9.2

有这样一个需求，给你任意一个字符串，把它转化为类,网上大多数的解决办法是下面三种:

Kernel.const_get(:User) # Object.const_get(:User)
eval(’User’)
‘User’.constantize

但是上面三种方法, 这个 User 事先必须是初始化的,不然会报错，如下:

Object.const_get(:User) # uninitialized constant User (NameError)

所以需要加个判断这个 Class 有没有初始化，没有的话再set 一个Class

require "rails/all"

def Kernel.const_missing(name)
  Object.const_set(name,Class.new)
end
#p Kernel.const_get("baoxiaos".to_sym) # wrong constant name baoxiaos (NameError)
p Kernel.const_get("baoxiaos".classify.to_sym) # Baoxiao , const的首字母必须大写
p Kernel.constants # []
p Object.constants.include?(:UBaoxiao) # true

刚开始把这个 const 定义在 Object 里:

require "rails/all"

def Object.const_missing(name)
  Object.const_set(name,Class.new)
end

#p Object.const_get("baoxiaos".to_sym) # wrong constant name baoxiaos (NameError)
p Object.const_get("baoxiaos".classify.to_sym)

发现用在 rails 中后 , rails 处处报错，可能怪我重写了 Object.const_missing 导致的 ……..

上面方法的原理是当找不到 const的时候执行了

  Object.const_set(name,Class.new)

那么 name 就变成是 Class 的实例了 , 为什么定义在 Kernel 中的 const_missing ，Object 也可以访问到，需要注意 Object,Kernel 之间的关系,Object 是 inluce Kernel 的,如下:

class Object
include Kernel
end

SEE:

http://niczsoft.com/2010/01/string-to-class-in-ruby-on-rails/
http://www.ruby-forum.com/topic/96222

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Rails try method

Posted by wxianfeng Fri, 14 Jan 2011 08:20:00 GMT

环境:ruby 1.9.2 + rails 3.0.3

我们经常会有这样的操作:

user = User.find_by_login("wxianfeng")  # =>  nil 
user.name # => NoMethodError: undefined method `name' for nil:NilClass

假如 login 为 wxianfeng 不存在，会报错:

NoMethodError: undefined method `name' for nil:NilClass

那么建议使用 try 方法避免报错，try 返回的是 nil

user.try(:name) # =>nil

也就相当于

nil.try(:name) # => nil

看下源码: here

其实就是调用了 __send__ 方法 , __send__ 方法和 send 方法等价 , 只不过 __send__ 方法为了防止有已经存在的 send 方法 , nil 的话调用 NilClass 的 try 方法

另外发现 github上 try方法已经重新写了，如下: here

class Object
  # Invokes the method identified by the symbol +method+, passing it any arguments
  # and/or the block specified, just like the regular Ruby <tt>Object#send</tt> does.
  #
  # *Unlike* that method however, a +NoMethodError+ exception will *not* be raised
  # and +nil+ will be returned instead, if the receiving object is a +nil+ object or NilClass.
  #
  # If try is called without a method to call, it will yield any given block with the object.
  #
  # ==== Examples
  #
  # Without try
  # @person && @person.name
  # or
  # @person ? @person.name : nil
  #
  # With try
  # @person.try(:name)
  #
  # +try+ also accepts arguments and/or a block, for the method it is trying
  # Person.try(:find, 1)
  # @people.try(:collect) {|p| p.name}
  #
  # Without a method argument try will yield to the block unless the reciever is nil.
  # @person.try { |p| "#{p.first_name} #{p.last_name}" }
  #--
  # +try+ behaves like +Object#send+, unless called on +NilClass+.
  def try(*a, &b)
    if a.empty? && block_given?
      yield self
    else
      __send__(*a, &b)
    end
  end
end

class NilClass #:nodoc:
  def try(*args)
    nil
  end
end

其实只是判断了 if a.empty? && block_given? 这种情况则直接执行block 内容然后返回，效果一样…..

DEMO:

require "active_support/core_ext/object/try"

class Klass

  def send(*args)
    "helo " + args.join(' ')
  end

  def hello(*args)
    "Hello " + args.join(' ')
  end

  def self.foobar(s)
     "#{s} foobar"
  end
end

k = Klass.new

# __send__ 为了防止有方法名叫send ， 建议用 __send__
p k.__send__ :hello, "gentle", "readers"   #=> "Hello gentle readers" 
p k.send "gentle", "readers"   #=> "Helo gentle readers"

# Ruby 里一切皆是对象,类也是对象
# Klass(类) 是 Class 的实例 , Class 是 Object 的实例 , 那么 Klass 也就是 Object 的实例 所以 Klass 可以调用try 方法
p Klass.try(:foobar,"hey") # => "hey foobar"
# k 是Klass 的实例,Klass 的父类是 Object , 所以 k 可以调用 try 方法
p k.try(:send,"bla","bla") # => "helo bla bla"

# class 得到的是 实例关系
# superclass 得到的是 继承关系
p Klass.superclass # Object
p Klass.class # Class
p k.class # Klass

另外这是对象nil 那如果没有那个字段了，就会报找不到方法的错误

例如:

ruby-1.9.2-p0 > u=User.first
  User Load (175.8ms)  SELECT `users`.* FROM `users` LIMIT 1
 => #<User id: 1, login: "entos", name: "", email: "entos@entos.com", crypted_password: "557c88b0713f63397249f4198368e4a57d6d400f", salt: "4e04ef1cf506595ac3edf6a249791c55995b0f8f", remember_token: nil, remember_token_expires_at: nil, activation_code: nil, activated_at: nil, status: 2, suspend_at: nil, avatar_id: nil, orgunit_id: nil, mobile_phone: nil, last_login_at: nil, language: nil, options: nil, created_at: "2011-02-24 02:55:42", updated_at: "2011-02-24 02:55:42"> 
ruby-1.9.2-p0 > u.hi
NoMethodError: undefined method `hi' for #<User:0x9fcfe00>

建议加上 respond_to? 判断

ruby-1.9.2-p0 > u.respond_to? "hi"
 => false

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rails 控制台输出sql

Posted by wxianfeng Fri, 14 Jan 2011 03:14:00 GMT

环境:ruby 1.9.2 + rails 3.0.3

我们经常需要在 rails console 中进行Model的操作,想看执行的sql ，必须到 rails log 中去查看，现在有一个更好的办法，直接输出到 console 中…

在console 运行下面这句话即可:

ActiveRecord::Base.logger = Logger.new(STDOUT)

或者直接写到 config/appliction.rb 中，下次启动console的时候不需要在写上面语句:

    if Rails.env == 'development'
      ActiveRecord::Base.logger = Logger.new(STDOUT)
    end

DEMO:

wxianfeng@ubuntu:/usr/local/system/projects/entos/ent_os$ rails  c 
Loading development environment (Rails 3.0.3)
ruby-1.9.2-p0 > ActiveRecord::Base.logger = Logger.new(STDOUT)
 => #<Logger:0xadc0730 @progname=nil, @level=0, @default_formatter=#<Logger::Formatter:0xadc071c @datetime_format=nil>, @formatter=nil, @logdev=#<Logger::LogDevice:0xadc06a4 @shift_size=nil, @shift_age=nil, @filename=nil, @dev=#<IO:<STDOUT>>, @mutex=#<Logger::LogDevice::LogDeviceMutex:0xadc0690 @mon_owner=nil, @mon_count=0, @mon_mutex=#<Mutex:0xadc0668>>>> 
ruby-1.9.2-p0 > User.last 
  User Load (0.2ms)  SELECT `users`.* FROM `users` ORDER BY users.id DESC LIMIT 1
 => #<User id: 15, login: "xxxxxx", name: "", email: "xx@zz.com", crypted_password: "471f98733c6d2456df58a354feddcf7af22ea78e", salt: "f03c284f91365a3eeb30a2898b79524694efdac5", remember_token: nil, remember_token_expires_at: nil, activation_code: nil, activated_at: "2011-01-07 08:00:25", status: 2, suspend_at: nil, avatar_id: nil, orgunit_id: nil, mobile_phone: nil, last_login_at: nil, language: nil, options: nil, created_at: "2011-01-07 08:00:17", updated_at: "2011-01-07 08:00:25">

另外还可以使用 hirb gem 来让输出格式以表格排列，个人不是太喜欢，原有的方式可以看出数据的返回格式,是集合数组，还是单个对象一清二楚。。。而hirb 就没有了

SEE：

http://tuohuang.thoughtworkers.org/?p=114

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Rails源码 attr_internal

Posted by wxianfeng Fri, 06 Jan 2012 07:34:00 GMT

环境:ruby 1.9.2 + rails 3.0.3 + ubuntu 10.10

params在rails中很常用，特别在表单提交的时候,params 产生的是一个Hash ，里面构造通过 form域的name构造 ,产生不同的 params 内容,今天在看rails params 实现的时候发现通过 attr_internal 的方法实现,params方法的源码:

    def params
      @_params ||= request.parameters
    end

发现其实是从 request 这个方法得到的,那么request方法又是怎么定义的:

attr_internal :headers, :response, :request

就是用了 attr_internal 方法

看下整个 metal.rb文件: here

发现了 response,headers,session(借助delegate委派) ,status,params == 都是通过 attr_internal 实现的,来看看 attr_internal 到底是何须人也：

源码： here

class Module
  # Declares an attribute reader backed by an internally-named instance variable.
  def attr_internal_reader(*attrs)
    attrs.each do |attr|
      module_eval "def #{attr}() #{attr_internal_ivar_name(attr)} end", __FILE__, __LINE__
    end
  end

  # Declares an attribute writer backed by an internally-named instance variable.
  def attr_internal_writer(*attrs)
    attrs.each do |attr|
      module_eval "def #{attr}=(v) #{attr_internal_ivar_name(attr)} = v end", __FILE__, __LINE__
    end
  end

  # Declares an attribute reader and writer backed by an internally-named instance
  # variable.
  def attr_internal_accessor(*attrs)
    attr_internal_reader(*attrs)
    attr_internal_writer(*attrs)
  end

  alias_method :attr_internal, :attr_internal_accessor

  class << self; attr_accessor :attr_internal_naming_format end
  self.attr_internal_naming_format = '@_%s'

  private
    def attr_internal_ivar_name(attr)
      Module.attr_internal_naming_format % attr
    end
end

发现其实就是通过 module_eval 给对象添加了 settet , getter 方法而已,但是命名格式是这样的:

  self.attr_internal_naming_format = '@_%s'

DEMO:

require "active_support/core_ext/module/attr_internal"

class Foo
  
  attr_accessor :sex,:birthday # attr_accessor ruby里封装的method
  attr_internal :name,:city # attr_internal rails 封装的

  def bar
    name # call getter method # => @_name
  end

end

f = Foo.new
f.name = 'wxianfeng'
p f.instance_variables # => [:@_name]
p f.name # => "wxianfeng"
p f # => #<Foo:0x8630e18 @_name="wxianfeng">
p f.bar # => "wxianfeng"

所以 attr_internal 和 attr_accessor 其实是等价的,只不过从字面意思上看是内部变量(闭包变量的写法) ，attr_internal 希望你通过方法名来调用，不用 @_%s 这个写法来调用

所以其实一般我们在 controller 用的 request 方法其实可以直接这样写 @_request ,

request #=> @_request
params # => @_request.parameters
params # => @_params
headers #=> @_headers
status #=> @_status
.
.
.

但是一般不建议这样写

还发现这些和 http相关的东西都定义在 metal 模块, metal 是 rails 链接 rack 的中间件,源码中的解释:

ActionController::Metal provides a way to get a valid Rack application from a controller.

Rack 是一个 ruby实现的web server,封装了 http的请求和响应等,例如 rails,sinatra == 都是在 rack 基础上实现的……

有机会很有必要深入学习下…

SEE:

http://rubyonrailswin.wordpress.com/2007/03/07/actioncontroller-and-what-the-heck-is-attr_internal/
http://www.oschina.net/p/rack

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capistrano 多机部署

正则 ?: 非捕获组

北京 798 Ruby/Rails 活动

shell 文件插入行

ruby yaml 表示数组

ruby rake tips

ruby string to class

Rails try method

rails 控制台输出sql

Rails源码 attr_internal