步骤1 － 安装 RVM

RVM 是干什么的这里就不解释了，后面你将会慢慢搞明白。

　　　　$ curl -L https://get.rvm.io | bash -s stable

期间可能会问你sudo管理员密码，这里可能需要等待一段时间后就可以成功安装好 RVM。

案例信息如下：

lihuifengdeMacBook-Pro:~ lihuifeng$ curl -L https://get.rvm.io | bash -s stable

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   184  100   184    0     0      8      0  0:00:23  0:00:21  0:00:02     8
100 22817  100 22817    0     0    523      0  0:00:43  0:00:43 --:--:--  1056
Downloading https://github.com/wayneeseguin/rvm/archive/1.26.10.tar.gz
Downloading https://github.com/wayneeseguin/rvm/releases/download/1.26.10/1.26.10.tar.gz.asc
Found PGP signature at: 'https://github.com/wayneeseguin/rvm/releases/download/1.26.10/1.26.10.tar.gz.asc',
but no GPG software exists to validate it, skipping.

Upgrading the RVM installation in /Users/lihuifeng/.rvm/
    RVM PATH line found in /Users/lihuifeng/.profile /Users/lihuifeng/.bashrc /Users/lihuifeng/.zshrc.
    RVM sourcing line found in /Users/lihuifeng/.bash_profile /Users/lihuifeng/.zlogin.
Upgrade of RVM in /Users/lihuifeng/.rvm/ is complete.

# lihuifeng,
#
#   Thank you for using RVM!
#   We sincerely hope that RVM helps to make your life easier and more enjoyable!!!
#
# ~Wayne, Michal & team.

In case of problems: http://rvm.io/help and https://twitter.com/rvm_io

Upgrade Notes:

  * No new notes to display.

－－这里就表示已经成功安装了－－

然后，载入 RVM 环境

　　　　$ source ~/.rvm/scripts/rvm

检查一下是否安装正确 ：输入命令   rvm -v ，如果正确会列出RVM版本 如下所示：

　　　 $ rvm -v
A RVM version 1.26.10 (latest) is installed yet 1.25.28 (stable) is loaded.
Please do one of the following:
  * 'rvm reload'
  * open a new shell
  * 'echo rvm_auto_reload_flag=1 >> ~/.rvmrc' # for auto reload with msg.
  * 'echo rvm_auto_reload_flag=2 >> ~/.rvmrc' # for silent auto reload.

步骤2 － 用 RVM 安装 Ruby 环境

  输入命令　　$ rvm install 2.0.0

　　　　$ rvm install 2.0.0

同样继续等待漫长的下载，编译过程，完成以后就安装好了。

A RVM version 1.26.10 (latest) is installed yet 1.25.28 (stable) is loaded.
Please do one of the following:
  * 'rvm reload'
  * open a new shell
  * 'echo rvm_auto_reload_flag=1 >> ~/.rvmrc' # for auto reload with msg.
  * 'echo rvm_auto_reload_flag=2 >> ~/.rvmrc' # for silent auto reload.

步骤3 － 设置 Ruby 版本

RVM 装好以后，需要执行下面的命令将指定版本的 Ruby 设置为系统默认版本

测试是否正确

　lihuifengdeMacBook-Pro:~ lihuifeng$ ruby -v
ruby 2.0.0p481 (2014-05-08 revision 45883) [x86_64-darwin13.1.0]
lihuifengdeMacBook-Pro:~ lihuifeng$ gem -v
2.2.2


这有可能是因为Ruby的默认源使用的是cocoapods.org，国内访问这个网址有时候会有问题，网上的一种解决方案是将远替换成淘宝的，替换方式如下：
　　   $gem source -r https://rubygems.org/
　　　　$ gem source -a https://ruby.taobao.org

lihuifengdeMacBook-Pro:~ lihuifeng$ gem source -r https://rubygems.org/
https://rubygems.org/ removed from sources
lihuifengdeMacBook-Pro:~ lihuifeng$ gem source -a https://ruby.taobao.org
https://ruby.taobao.org added to sources

 要想验证是否替换成功了，可以执行：

　　　　$ gem sources -l  

正常的输出结果：

这里就表示已经把Ruby环境成功的安装到了Mac 上了。