CocoaPodsのインストールについてのメモ

http://qiita.com/satoken0417/items/479bcdf91cff2634ffb1
において、

sudo gem install cocoapods

でつまづく。以下エラー文。

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

以下のように、rbenvのバージョンを >= 2.2.2.になるようにしたが効果無し。

kimuraryouyuu-no-MacBook-Air:~ Ryosuke$ rbenv versions
  system
  2.2.0
* 2.2.3 (set by /Users/Ryosuke/.rbenv/version)

よくよく調べてみると、gemにおけるRUBY VERSIONが2.0.0であった。(もはやgemとrbenvの違いがわかってない汗)

kimuraryouyuu-no-MacBook-Air:~ Ryosuke$ gem environment
RubyGems Environment:
  - RUBYGEMS VERSION: 2.6.6
  - RUBY VERSION: 2.0.0 (2014-05-08 patchlevel 481) [universal.x86_64-darwin13]
  - INSTALLATION DIRECTORY: /Library/Ruby/Gems/2.0.0
  - USER INSTALLATION DIRECTORY: /Users/Ryosuke/.gem/ruby/2.0.0
  - RUBY EXECUTABLE: /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
  - EXECUTABLE DIRECTORY: /usr/bin
  - SPEC CACHE DIRECTORY: /Users/Ryosuke/.gem/specs
  - SYSTEM CONFIGURATION DIRECTORY: /Library/Ruby/Site
  - RUBYGEMS PLATFORMS:
    - ruby
    - universal-darwin-13
  - GEM PATHS:
     - /Library/Ruby/Gems/2.0.0
     - /Users/Ryosuke/.gem/ruby/2.0.0
     - /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/gems/2.0.0
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - https://rubygems.org/
  - SHELL PATH:
     - /Users/Ryosuke/anaconda/bin
     - /Library/Frameworks/Python.framework/Versions/3.5/bin
     - /Users/Ryosuke/Library/Enthought/Canopy_64bit/User/bin
     - /Library/Frameworks/Python.framework/Versions/2.7/bin
     - /usr/bin
     - /bin
     - /usr/sbin
     - /sbin
     - /usr/local/bin
     - /opt/X11/bin
     - /usr/local/git/bin

RUBY VERSIONを上げる方法がわからなかったので、
シンプルに「ERROR: Error installing cocoapods: activesupport requires Ruby version >= 2.2.2.」と検索してみると
https://github.com/CocoaPods/CocoaPods/issues/4711

が見つかり、

sudo gem install activesupport -v 4.2.6

をして無事にcocoapodsをインストールできました。