kakaxi2 (kakaxi2)

bin/rails server 启动过程中遇到 LoadError 异常

kakaxi2 — Sun, 03 Jul 2016 14:23:54 +0800

环境 CentOS7 ruby 2.0.0p598 (2014-11-13) [x86_64-linux] rails (4.2.0) gem( 2.0.14)

在创建好 rail 应用后，执行 bin/rails server 时报告如下的错误，stackoverflow 查看说这个问题在 windows 环境由于 nokogiri 兼容性问题经常出现，但是没有 linux 环境问题出现这种情况的资料，请谁遇到的话帮忙解答一下。

Warning: You're using Rubygems 2.0.14 with Spring. Upgrade to at least Rubygems 2.1.0 and run `gem pristine --all` for better startup performance.
/usr/local/share/gems/gems/nokogiri-1.6.8/lib/nokogiri.rb:32:in `require': cannot load such file -- nokogiri/nokogiri (LoadError)
    from /usr/local/share/gems/gems/nokogiri-1.6.8/lib/nokogiri.rb:32:in `rescue in <top (required)>'
    from /usr/local/share/gems/gems/nokogiri-1.6.8/lib/nokogiri.rb:28:in `<top (required)>'
    from /usr/local/share/gems/gems/loofah-2.0.3/lib/loofah.rb:3:in `require'
    from /usr/local/share/gems/gems/loofah-2.0.3/lib/loofah.rb:3:in `<top (required)>'
    from /usr/local/share/gems/gems/rails-html-sanitizer-1.0.3/lib/rails-html-sanitizer.rb:2:in `require'
    from /usr/local/share/gems/gems/rails-html-sanitizer-1.0.3/lib/rails-html-sanitizer.rb:2:in `<top (required)>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/sanitize_helper.rb:3:in `require'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/sanitize_helper.rb:3:in `<top (required)>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/text_helper.rb:32:in `<module:TextHelper>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/text_helper.rb:29:in `<module:Helpers>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/text_helper.rb:6:in `<module:ActionView>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/text_helper.rb:4:in `<top (required)>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/form_tag_helper.rb:18:in `<module:FormTagHelper>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/form_tag_helper.rb:14:in `<module:Helpers>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/form_tag_helper.rb:8:in `<module:ActionView>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/form_tag_helper.rb:6:in `<top (required)>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/form_helper.rb:4:in `require'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers/form_helper.rb:4:in `<top (required)>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers.rb:50:in `<module:Helpers>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers.rb:4:in `<module:ActionView>'
    from /usr/local/share/gems/gems/actionview-4.2.0/lib/action_view/helpers.rb:3:in `<top (required)>'
    from /usr/local/share/gems/gems/sprockets-rails-3.1.1/lib/sprockets/rails/context.rb:7:in `<module:Context>'
    from /usr/local/share/gems/gems/sprockets-rails-3.1.1/lib/sprockets/rails/context.rb:6:in `<module:Rails>'
    from /usr/local/share/gems/gems/sprockets-rails-3.1.1/lib/sprockets/rails/context.rb:5:in `<module:Sprockets>'
    from /usr/local/share/gems/gems/sprockets-rails-3.1.1/lib/sprockets/rails/context.rb:4:in `<top (required)>'
    from /usr/local/share/gems/gems/sprockets-rails-3.1.1/lib/sprockets/railtie.rb:7:in `require'
    from /usr/local/share/gems/gems/sprockets-rails-3.1.1/lib/sprockets/railtie.rb:7:in `<top (required)>'
    from /home/sdy/.gem/ruby/gems/sass-rails-5.0.5/lib/sass/rails/railtie.rb:3:in `require'
    from /home/sdy/.gem/ruby/gems/sass-rails-5.0.5/lib/sass/rails/railtie.rb:3:in `<top (required)>'
    from /home/sdy/.gem/ruby/gems/sass-rails-5.0.5/lib/sass/rails.rb:11:in `require'
    from /home/sdy/.gem/ruby/gems/sass-rails-5.0.5/lib/sass/rails.rb:11:in `<top (required)>'
    from /home/sdy/.gem/ruby/gems/sass-rails-5.0.5/lib/sass-rails.rb:1:in `require'
    from /home/sdy/.gem/ruby/gems/sass-rails-5.0.5/lib/sass-rails.rb:1:in `<top (required)>'
    from /usr/local/share/gems/gems/bundler-1.12.5/lib/bundler/runtime.rb:86:in `require'
    from /usr/local/share/gems/gems/bundler-1.12.5/lib/bundler/runtime.rb:86:in `block (2 levels) in require'
    from /usr/local/share/gems/gems/bundler-1.12.5/lib/bundler/runtime.rb:81:in `each'
    from /usr/local/share/gems/gems/bundler-1.12.5/lib/bundler/runtime.rb:81:in `block in require'
    from /usr/local/share/gems/gems/bundler-1.12.5/lib/bundler/runtime.rb:70:in `each'
    from /usr/local/share/gems/gems/bundler-1.12.5/lib/bundler/runtime.rb:70:in `require'
    from /usr/local/share/gems/gems/bundler-1.12.5/lib/bundler.rb:102:in `require'
    from /home/sdy/railsworkspace/blog/config/application.rb:7:in `<top (required)>'
    from /usr/local/share/gems/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:78:in `require'
    from /usr/local/share/gems/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:78:in `block in server'
    from /usr/local/share/gems/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:75:in `tap'
    from /usr/local/share/gems/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:75:in `server'
    from /usr/local/share/gems/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
    from /usr/local/share/gems/gems/railties-4.2.0/lib/rails/commands.rb:17:in `<top (required)>'
    from /home/sdy/railsworkspace/blog/bin/rails:9:in `require'
    from /home/sdy/railsworkspace/blog/bin/rails:9:in `<top (required)>'
    from /home/sdy/.gem/ruby/gems/spring-1.7.2/lib/spring/client/rails.rb:28:in `load'
    from /home/sdy/.gem/ruby/gems/spring-1.7.2/lib/spring/client/rails.rb:28:in `call'
    from /home/sdy/.gem/ruby/gems/spring-1.7.2/lib/spring/client/command.rb:7:in `call'
    from /home/sdy/.gem/ruby/gems/spring-1.7.2/lib/spring/client.rb:30:in `run'
    from /home/sdy/.gem/ruby/gems/spring-1.7.2/bin/spring:49:in `<top (required)>'
    from /home/sdy/.gem/ruby/gems/spring-1.7.2/lib/spring/binstub.rb:11:in `load'
    from /home/sdy/.gem/ruby/gems/spring-1.7.2/lib/spring/binstub.rb:11:in `<top (required)>'
    from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /home/sdy/railsworkspace/blog/bin/spring:13:in `<top (required)>'
    from bin/rails:3:in `load'
    from bin/rails:3:in `<main>'

一个 shell 运算的语法小问题，求解答一下

kakaxi2 — Mon, 19 Oct 2015 10:15:33 +0800

function getTiming() {  
    start=$1  
    end=$2  

    start_s=$(echo $start | cut -d '.' -f 1)  
    start_ns=$(echo $start | cut -d '.' -f 2)  
    end_s=$(echo $end | cut -d '.' -f 1)  
    end_ns=$(echo $end | cut -d '.' -f 2)  

    time=$(( ( 10#$end_s - 10#$start_s ) * 1000 + ( 10#$end_ns / 1000000 - 10#$start_ns / 1000000 ) ))  


    echo "$time ms"  
}

其中的 time 开始的这一行当中的10#的作用是？

对于继承了 ActiveRecord::Base 来创建模型的类，想要修改对应字段的 set 和 get 方法

kakaxi2 — Mon, 05 Oct 2015 16:52:03 +0800

初学者，想要写一个 model，主要是用来记录用户名和密码，现在的目的是为了给 password 进行 hash 转换，按我的理解 ActiveRecord::Base 是起到了 attr_accessor 的作用，不知道如下的写法是否存在了纰漏？存在问题，可以设置 password，但是 valid 为 false，求解。

class User < ActiveRecord::Base
    validates :name, presence: true
    validates :password, presence: true

    def password
        @password
    end

    def password=(password)
        puts "here"
        return if not password
        password = generatePassword(password)
        super(password)
    end

    private
    def generatePassword(password)
        Digest::SHA256.hexdigest(password)
    end
end

关于 Rails 的数据库配置文件 database.yml 当中，Yaml 的表达式解释的问题，查阅了一些资料还是没有了解

kakaxi2 — Sun, 04 Oct 2015 11:48:45 +0800

# SQLite version 3.x
#   gem install sqlite3
#
#   Ensure the SQLite 3 gem is defined in your Gemfile
#   gem 'sqlite3'
#
default: &default
  adapter: sqlite3
  pool: 5
  timeout: 5000

development:
  <<: *default
  database: db/development.sqlite3

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  <<: *default
  database: db/test.sqlite3

production:
  <<: *default
  database: db/production.sqlite3

其中&default定义了引动点，*defalut进行了引用，不明白的地方在于符号<<:的作用是什么？

关于一个 Sed 命令的，谁能来解释一下

kakaxi2 — Tue, 15 Sep 2015 13:37:09 +0800

需要写一个下载网页图片的 shell 脚本，网上看到一个例子，但是对于如下的这条 sed 命令，其表达的意思，谁能来解释一下：

sed -i "s|^/|$baseurl/|" /tmp/$$.list

Nginx + Passenger 部署 Rails，希望能够直接访问 Rails 的 public 目录的静态文件，但是 Nginx 总是返回 404

kakaxi2 — Sun, 09 Aug 2015 18:29:40 +0800

是这样的，我按照配置，给出了如下的 nginx 的配置文件，

events {
    worker_connections  1024;
}

http {
    passenger_root /home/sdy/.rvm/gems/ruby-2.0.0-p643@rails4/gems/passenger-5.0.15;
    passenger_ruby /home/sdy/.rvm/gems/ruby-2.0.0-p643@rails4/wrappers/ruby;

    include       mime.types;
    default_type  application/octet-stream;

    #access_log  logs/access.log  main;

    sendfile        on;
    keepalive_timeout  65;

    server {
        listen 8800;
        server_name 127.0.0.1;
        root /home/sdy/rails_project/saler/public;
        passenger_intercept_errors on;
        passenger_friendly_error_pages off;
        passenger_enabled on;
        error_page 404  /404.html;
     }
}

目的是：

希望能够直接访问 rails 的静态资源，包括 html,css,js 等。到目前为止，我的理解是如果在 rails 项目的 public 目录能够访问到的，nginx 应该能够直接返回，但是 nginx 启动后提示 404 找不到页面
希望能够使用 public 目录当中定制的 404 页面，访问http://127.0.0.1/abc.html

查看 nginx 的日志显示为：

2015/08/09 18:15:02 [error] 12945#0: *3 open() "/home/sdy/rails_project/saler/public/abc.html" failed (2: No such file or directory), client: 127.0.0.1, server: 127.0.0.1, request: "GET /abc.html HTTP/1.1", host: "127.0.0.1:8800" 

2015/08/09 18:15:02 [error] 12945#0: *3 open() "/home/sdy/rails_project/saler/public/404.html" failed (2: No such file or directory), client: 127.0.0.1, server: 127.0.0.1, request: "GET /abc.html HTTP/1.1", host: "127.0.0.1:8800"

我的 public 目录当中是存在 abc.html 以及 404.html 的，可以判断 nginx 访问 public 目录没有找到 abc.html，随后按照设置在该目录寻找 404.html 但是都没有找到

疑问是：

passenger 在 nginx 当中是怎么配置使得访问静态资源直接有 nginx 来返回，动态资源有 rails 来返回的。
上述的访问http://127.0.0.1/abc.htmldevelopment环境当中是可以，但是production环境当中就不行，为何在？
public 目录不是说是 rails 路由一开始就能直接看到的么，然后如果在 public 目录找不到文件才去走 routes.rb，但是 production 和 nginx 都访问不到 abc.html.

附注：rails 使用的是 4.2，我猜是不是和 asset 之类的有关，但是 asset 这不是我不是很懂。

初学者的关于部署 Rails 的问题

kakaxi2 — Tue, 14 Jul 2015 16:16:37 +0800

作为一个 rails 的初学者，我想问一下，为什么网上给的部署 Rails 的时候的配置方案，大多数都是用一个前端服务器（比如 Apache 或者 nginx）加上一个后端的服务器（比如 Thin，unicorn）之类的来完成配置，我想问的是如果我不需要负载均衡，只需要一个开一个 Thin 服务就够了，那么直接把 Thin 挂到前端，就是又当前端，又当后端，这样可以么？

关于 Ruby 复杂的类体系结构的思考

kakaxi2 — Sun, 24 May 2015 18:19:58 +0800

刚刚开始学习使用 ruby on rails，也在学习使用 ruby 的方方面面，感觉要了解 ruby 的类的体系结构还是得花一些心思，有点复杂啊。我感觉主要是你要从类和对象两个角度来看一个类，不同于其他的面向对象语言，ruby 里的类即是类，也是对象。

Class 是除了 Kernel 以外的任何类（现在我们应该从对象的角度），类与对象的联系，类的视力