没用过，猜测 如果是 RVM /home/your_name/.rvm/wrappers/default/ruby;

和 2 不同，以public/uploads为例 set :linked_dirs, fetch(:linked_dirs) + %w{public/system public/uploads}

#8 楼 @angelfan 没在 windows 下玩过 rails

#5 楼 @ashchan :plus1:

def g_salt(len)
  chars = ("a".."z").to_a + ("A".."Z").to_a + ("0".."9").to_a
  salt = ""
  1.upto(len) {|i| salt << chars[rand(chars.size-1)]}
  salt
end

g_salt 4

我也折腾过一阵。最大的感触是 ejabberd 没有 erlang 大牛就别去折腾了。openfire 倒是可以，但是大家都说集群支持差，没实践过。如果只是作为一个模块，第三方服务方便。

那些钩子方法全部在事务里面，出问题会回滚，对于第一块代码，有两种方法 第一种是改变逻辑，先判断是不是为 1 第二种是把 begin 和 rescue 之间的代码写在事务里面User.transaction do ... end

首先你的逻辑有问题吧，删除了再判断，然后来一个cant delete last user!!! 其次：

def destroy
   begin
     @user.destroy   
     flash[:notice] = "User #{@user.name} deleted"
     if User.count.zero?   # 1 如果这里确实为ture
       raise 'cant delete last user' # 2 那么这里异常会调到rescue
     end # 3
   rescue StandardError => e # rescue Exception => e
     flash[:notice] = e.message # 那么这里就会执行
   end
   respond_to do |format| # 正常执行
     format.html { redirect_to users_url }
     format.json { head :no_content }
   end
 end

我猜测是不是 StandardError 的问题，报什么错你没说。换顶层的Exception => e试下

simple_form 没用过 你可以谷歌下省市区级联菜单 1.可以全部前段搞定，见 qq 的 ip 查询那个页面的做法 2.可以把省市区保存到后台文件或者数据库，然后 ajax

#2 楼 @dfguo 文件没了。百度云吧

#6 楼 @42thcoder thx! http://www.rubydoc.info/github/websocket-rails/websocket-rails/WebsocketRails#users-class_method https://github.com/websocket-rails/websocket-rails/issues/164

#3 楼 @42thcoder 可以直接收到 A 的消息, 然后转发给 B 的. 这里就是关键，我可能转发给 B, 也可能转发给 BCDEF......问题就是怎么去转发，我可以识别是哪个发来的 (在 message 里面带 username).但是我看到的 websocket 实现除了 socket.io 有from和to,其他都没有。

#1 楼 @zhang_soledad 谢谢。我的目的其实不是推送。而是 one to one 的聊天。如果用 pub/sub 实现那就是 1:1，我觉得这样做不值得。换句话说，我想用 websocket 或者 amqp 等其他一些协议来实现 1 对 1 的聊天。

name = name.encode('gb2312', 'utf-8')

看你需求罗，如果以后不直接修改 markdown，就都可以，如果需要修改，那就后台。

gorails.com 有一节专门讲这个，jquery-ujs 那一节，具体的不在电脑操作不便。

#5 楼 @billy 我也觉得。据说淘宝改 java 是业务支撑不下去，不知道这里是为什么？很多东西能跑，不容易出错就阿弥陀佛啦。

#4 楼 @itomato +1 rails 4 不推荐 find 了，推荐 where

class HomeController < ApplicationController
  def index
    @new_3_projects = Project.all.last(3)
    @staff_pick_project = Project.first
  end
end

Atom编辑器, 可以带你装X, 不能带你飞

预备加上

我找了下，首先查找 libmysqlclient.so.16 文件，如果有就ldd,没有就安装他，如下: https://gettechgo.wordpress.com/2012/12/03/failed-dependency-libmysqlcliet-so-16/ 原文: While installing‘mysql’module for PHP 5.4 (yum install php54w-mysql*), I encountered the following error:

Missing Dependency: libmysqlclient.so.16(libmysqlclient_16) is needed by package php-mysql-package-version

The issue was due to the “Missing Dependency” and a library called “libmysqlclient.so.16″ was required.

To resolve this, I downloaded a “compat” rpm, and installed all the different versions of libmysqlclient.so.{12,14,15,16}:

Available at: http://downloads.mysql.com/archives/mysql-5.1/MySQL-shared-compat-5.1.49-1.rhel5.x86_64.rpm

wget "http://downloads.mysql.com/archives/mysql-5.1/MySQL-shared-compat-5.1.49-1.rhel5.x86_64.rpm"

rpm -ivh MySQL-shared-compat-5.1.49-1.rhel5.x86_64.rpm

After that, ‘mysql’ module got installed with PHP 5.4 properly.

#6 楼 @angelfan websocket-rails project: http://websocket-rails.github.io/ demo: https://github.com/YavorK/websocket-rails-demo-light

之前听说取消了，我去官网看也没有

我意见是 ruby 就别当 java 用了，复杂业务直接 java 的好。另事务是个大问题。

一。网上搜索的，看着靠谱，但是得删除数据库服务器重装 The above problem will be occured because the mysql-devel package is not properly installed in your system. I will be explain the same in Centos of how to fix it. When you try to install that package using,

yum install mysql-devel

somtimes there will be some clash occurs with the existing packages that gets installed if you install the MySql-Administrative tool and MySQL query browser.

In that case, you need to uninstall all the existing mysql2 packages and install it again.

rpm -qa -last | grep -i mysql
yum remove MySQL-server-5.5.27-1.rhel5
yum remove MySQL-client-5.5.27-1.rhel5
yum remove mysql-gui-tools-5.0r12-1rhel4
yum remove mysql-query-browser-5.0r12-1rhel4-a

So, you can uninstall whatever mysql things displayed with rpm -qa as like above.

Then you can install the mysql-server and mysql-client.

yum install mysql-server
yum install mysql-client

Now you do the installation of mysql-devel package.

yum install mysql-devel

Now there is no package clashes and you can able to install the mysql2 gem.

gem install mysql2 -v '0.3.11'

Now your mysql2 gem will be successfully installed and you are good to go.

http://stackoverflow.com/questions/3754662/errors-installing-mysql2-gem-via-the-bundler

二。不用重装，但不知道能不能行

wget http://cdn.mysql.com/Downloads/MySQL-5.5/MySQL-devel-5.5.27-1.el6.x86_64.rpm 

rpm -Uvh MySQL-devel-5.5.27-1.el6.x86_64.rpm 

gem install mysql 

gem install mysql2

http://stackoverflow.com/questions/12119567/mysql2-gem-installation-fails