cocoapods的安装 遇到 Error installing

错误提示：

Error installing cocoapods:  activesupport requires Ruby version >= 2.2.2.

解决方案 ：

1、安装 RVM baby 版本管理器

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

//安装完成提示如下信息

In case of problems: https://rvm.io/helpandhttps://twitter.com/rvm_io

2、执行

$source ~/.bashrc

$source ~/.bash_profile

3、查看版本

$rvm -v

//提示以下信息

rvm 1.27.0 (latest) by Wayne E. Seguin, Michal Papis[https://rvm.io/]

4、用RVM升级Ruby查看当前ruby版本

$ruby -v

$rvm list known

//提示以下信息

# MRI Rubies

[ruby-]1.8.6[-p420]

[ruby-]1.8.7[-head] # security released on head

[ruby-]1.9.1[-p431]

[ruby-]1.9.2[-p330]

[ruby-]1.9.3[-p551]

[ruby-]2.0.0[-p648]

[ruby-]2.1[.8]

[ruby-]2.2[.4]

[ruby-]2.3[.0]

[ruby-]2.2-head

ruby-head

# for forks use: rvm install ruby-head- --url https://github.com/github/ruby.git --branch 2.2

5、安装ruby 2.2.2 执行

$rvm install 2.2.2

如果打印：

promote:~ shefeng$ rvm install 2.2.2

Searching for binary rubies, this might take some time.

Found remote file https://rvm_io.global.ssl.fastly.net/binaries/osx/10.11/x86_64/ruby-2.2.2.tar.bz2

Checking requirements for osx.

Certificates in '/usr/local/etc/openssl/cert.pem' are already up to date.

Requirements installation successful.

ruby-2.2.2 - #configure

ruby-2.2.2 - #download

% Total% Received % XferdAverage SpeedTimeTimeTimeCurrent

DloadUploadTotalSpentLeftSpeed

100 6854k100 6854k00126k00:00:540:00:54 --:--:--336k

ruby-2.2.2 - #validate archive

ruby-2.2.2 - #extract

ruby-2.2.2 - #validate binary

ruby-2.2.2 - #setup

ruby-2.2.2 - #gemset created /Users/shefeng/.rvm/gems/ruby-2.2.2@global

ruby-2.2.2 - #importing gemset /Users/shefeng/.rvm/gemsets/global.gems.........-

ruby-2.2.2 - #generating global wrappers........

ruby-2.2.2 - #gemset created /Users/shefeng/.rvm/gems/ruby-2.2.2

ruby-2.2.2 - #importing gemsetfile /Users/shefeng/.rvm/gemsets/default.gems evaluated to empty gem list

ruby-2.2.2 - #generating default wrappers........

Updating certificates in '/etc/openssl/cert.pem'.

mkdir: /etc/openssl: Permission denied

mkdir -p "/etc/openssl" failed, retrying with sudo

shefeng password required for 'mkdir -p /etc/openssl':

and sudo mkdir worked

则说明安装成功了

6、设置默认版本

$ rvm use 2.2.2 --default

提示一下信息即成功

Using /Users/shefeng/.rvm/gems/ruby-2.2.2