關於安裝cocoapods遇到的一些坑（ERROR: Error installing cocoapods: activesupport requires Ruby version >= 2.2）...

#出錯原因：Ruby版本較低 需要升級 或者未安裝Ruby版本

1.移除現有的Ruby

終端輸入：gem sources --remove https://rubygems.org/

2.使用淘寶映象

終端輸入：gem sources -a https://ruby.taobao.org/

3.驗證當前ruby版本

終端輸入：gem sources -l

成功後提示：

*** CURRENT SOURCES ***

https://ruby.taobao.org/

4.開始安裝cocoapods

終端輸入：sudo gem install cocoa pods

這時候提示：

Fetching: i18n-0.7.0.gem (100%)
Successfully installed i18n-0.7.0
Fetching: thread_safe-0.3.5.gem (100%)
Successfully installed thread_safe-0.3.5
Fetching: tzinfo-1.2.2.gem (100%)
Successfully installed tzinfo-1.2.2
Fetching: minitest-5.9.0.gem (100%)
Successfully installed minitest-5.9.0
Fetching: concurrent-ruby-1.0.2.gem (100%)
Successfully installed concurrent-ruby-1.0.2
Fetching: activesupport-5.0.0.gem (100%)
ERROR:  Error installing cocoapods:
activesupport requires Ruby version >= 2.2.2.
這個地方很坑，之前安裝cocoapods一直是沒有這個問題的，這裡提示Ruby版本要大於或等於2.2.2

於是檢視ruby版本

終端輸入：ruby -v

ruby 2.0.0p648 (2015-12-16 revision 53162) [universal.x86_64-darwin15]

果然這裡就要升級Ruby版本啦

檢視目前的所有ruby版本：

終端輸入：rvm list known

如果提示command not found 請先安裝rvm

終端輸入：curl -L get.rvm.io | bash -s stable  

如果已安裝會列出所有的ruby版本：

# 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-<name> --url https://github.com/github/ruby.git --branch 2.2

# JRuby
jruby-1.6[.8]
jruby-1.7[.23]
jruby[-9.0.5.0]
jruby-head

# Rubinius
rbx-1[.4.3]
rbx-2.3[.0]
rbx-2.4[.1]
rbx[-2.5.8]
rbx-head

# Opal
opal

# Minimalistic ruby implementation - ISO 30170:2012
mruby[-head]

# Ruby Enterprise Edition
ree-1.8.6
ree[-1.8.7][-2012.02]

# GoRuby
goruby

# Topaz
topaz

# MagLev
maglev[-head]
maglev-1.0.0

# Mac OS X Snow Leopard Or Newer
macruby-0.10
macruby-0.11
macruby[-0.12]
macruby-nightly
macruby-head

# IronRuby
ironruby[-1.1.3]
ironruby-head

這裡我們安裝2.2.2:

終端輸入：rvm install 2.2.2

終端執行結果：（如果直接成功請繞過homebrew的解除安裝安裝）

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.
About to install Homebrew, press `Enter` for default installation in `/usr/local`,
type new path if you wish custom Homebrew installation (the path needs to be writable for user)
: 

回車：(注意：一定要回車)

It appears Homebrew is already installed. If your intent is to reinstall you
should do the following before running this installer again:
    ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"
The current contents of /usr/local are .git
Requirements installation failed with status: 1.

這裡執行：

終端輸入：ruby -e "$(curl -fsSL 

https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"
解除安裝home-brew
Warning: This script will remove:
/Library/Caches/Homebrew/
/usr/local/.git/
Are you sure you want to uninstall Homebrew? [y/N] y
==> Removing Homebrew installation...
==> Removing empty directories...
==> Homebrew uninstalled!
You may want to restore /usr/local's original permissions
  sudo chmod 0755 /usr/local
  sudo chgrp wheel /usr/local

再執行：

終端輸入：rvm install 2.2.2

提示：

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.
About to install Homebrew, press `Enter` for default installation in `/usr/local`,
type new path if you wish custom Homebrew installation (the path needs to be writable for user)
: 

按回車：(注意：一定要回車)

==> This script will install:
/usr/local/bin/brew
/usr/local/Library/...
/usr/local/share/doc/homebrew
/usr/local/share/man/man1/brew.1
/usr/local/share/zsh/site-functions/_brew
/usr/local/etc/bash_completion.d/brew

Press RETURN to continue or any other key to abort
==> /usr/bin/sudo /bin/mkdir /Library/Caches/Homebrew

Password: （終端輸入密碼）
這裡需要輸入電腦密碼：

==> /usr/bin/sudo /bin/chmod g+rwx /Library/Caches/Homebrew
==> /usr/bin/sudo /usr/sbin/chown haha /Library/Caches/Homebrew
==> Downloading and installing Homebrew...
remote: Counting objects: 501, done.
remote: Compressing objects: 100% (445/445), done.
remote: Total 501 (delta 29), reused 360 (delta 27), pack-reused 0
Receiving objects: 100% (501/501), 787.83 KiB | 169.00 KiB/s, done.
Resolving deltas: 100% (29/29), done.
From https://github.com/Homebrew/brew
 * [new branch]      master     -> origin/master
HEAD is now at 32f7e73 download_strategy: ensure fixed commit hash length
==> Tapping homebrew/core
Cloning into '/usr/local/Library/Taps/homebrew/homebrew-core'...
remote: Counting objects: 3714, done.
remote: Compressing objects: 100% (3598/3598), done.
remote: Total 3714 (delta 14), reused 2112 (delta 6), pack-reused 0
Receiving objects: 100% (3714/3714), 2.88 MiB | 240.00 KiB/s, done.
Resolving deltas: 100% (14/14), done.
Checking connectivity... done.
Checking out files: 100% (3717/3717), done.
Tapped 3591 formulae (3,740 files, 9.0M)
==> Installation successful!
==> Next steps
Run `brew help` to get started
Further documentation: https://git.io/brew-docs
==> Homebrew has enabled anonymous aggregate user behaviour analytics
Read the analytics documentation (and how to opt-out) here:
  https://git.io/brew-analytics
Installing requirements for osx.
Updating system.....
Installing required packages: autoconf, automake, libtool, pkg-config, libyaml, readline, libksba, openssl........
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 % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 6854k  100 6854k    0     0  61342      0  0:01:54  0:01:54 --:--:--  132k
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/haha/.rvm/gems/ruby-2.2.2@global
ruby-2.2.2 - #importing gemset /Users/haha/.rvm/gemsets/global.gems..............................
ruby-2.2.2 - #generating global wrappers........
ruby-2.2.2 - #gemset created /Users/haha/.rvm/gems/ruby-2.2.2
ruby-2.2.2 - #importing gemsetfile /Users/haha/.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
haha password required for 'mkdir -p /etc/openssl': 
and sudo mkdir worked

這樣ruby2.2.2就安裝好了

現在就可以安裝cocoapods啦：

終端輸入：sudo gem install cocoa pods

看看這樣cocoapods就安裝成功了

Fetching: nap-1.1.0.gem (100%)
Successfully installed nap-1.1.0
Fetching: fourflusher-0.3.2.gem (100%)
Successfully installed fourflusher-0.3.2
Fetching: escape-0.0.4.gem (100%)
Successfully installed escape-0.0.4
Fetching: colored-1.2.gem (100%)
Successfully installed colored-1.2
Fetching: concurrent-ruby-1.0.2.gem (100%)
Successfully installed concurrent-ruby-1.0.2
Fetching: thread_safe-0.3.5.gem (100%)
Successfully installed thread_safe-0.3.5
Fetching: tzinfo-1.2.2.gem (100%)
Successfully installed tzinfo-1.2.2
Fetching: i18n-0.7.0.gem (100%)
Successfully installed i18n-0.7.0
Fetching: activesupport-5.0.0.gem (100%)
Successfully installed activesupport-5.0.0
Fetching: claide-1.0.0.gem (100%)
Successfully installed claide-1.0.0
Fetching: xcodeproj-1.1.0.gem (100%)
Successfully installed xcodeproj-1.1.0
Fetching: molinillo-0.4.5.gem (100%)
Successfully installed molinillo-0.4.5
Fetching: cocoapods-try-1.0.0.gem (100%)
Successfully installed cocoapods-try-1.0.0
Fetching: netrc-0.7.8.gem (100%)
Successfully installed netrc-0.7.8
Fetching: cocoapods-trunk-1.0.0.gem (100%)
Successfully installed cocoapods-trunk-1.0.0
Fetching: cocoapods-stats-1.0.0.gem (100%)
Successfully installed cocoapods-stats-1.0.0
Fetching: cocoapods-search-1.0.0.gem (100%)
Successfully installed cocoapods-search-1.0.0
Fetching: cocoapods-plugins-1.0.0.gem (100%)
Successfully installed cocoapods-plugins-1.0.0
Fetching: cocoapods-downloader-1.0.1.gem (100%)
Successfully installed cocoapods-downloader-1.0.1
Fetching: cocoapods-deintegrate-1.0.0.gem (100%)
Successfully installed cocoapods-deintegrate-1.0.0
Fetching: fuzzy_match-2.0.4.gem (100%)
Successfully installed fuzzy_match-2.0.4
Fetching: cocoapods-core-1.0.1.gem (100%)
Successfully installed cocoapods-core-1.0.1
Fetching: cocoapods-1.0.1.gem (100%)
Successfully installed cocoapods-1.0.1
Parsing documentation for nap-1.1.0
Installing ri documentation for nap-1.1.0
Parsing documentation for fourflusher-0.3.2
Installing ri documentation for fourflusher-0.3.2
Parsing documentation for escape-0.0.4
Installing ri documentation for escape-0.0.4
Parsing documentation for colored-1.2
Installing ri documentation for colored-1.2
Parsing documentation for concurrent-ruby-1.0.2
Installing ri documentation for concurrent-ruby-1.0.2
Parsing documentation for thread_safe-0.3.5
Installing ri documentation for thread_safe-0.3.5
Parsing documentation for tzinfo-1.2.2
Installing ri documentation for tzinfo-1.2.2
Parsing documentation for i18n-0.7.0
Installing ri documentation for i18n-0.7.0
Parsing documentation for activesupport-5.0.0
Installing ri documentation for activesupport-5.0.0
Parsing documentation for claide-1.0.0
Installing ri documentation for claide-1.0.0
Parsing documentation for xcodeproj-1.1.0
Installing ri documentation for xcodeproj-1.1.0
Parsing documentation for molinillo-0.4.5
Installing ri documentation for molinillo-0.4.5
Parsing documentation for cocoapods-try-1.0.0
Installing ri documentation for cocoapods-try-1.0.0
Parsing documentation for netrc-0.7.8
Installing ri documentation for netrc-0.7.8
Parsing documentation for cocoapods-trunk-1.0.0
Installing ri documentation for cocoapods-trunk-1.0.0
Parsing documentation for cocoapods-stats-1.0.0
Installing ri documentation for cocoapods-stats-1.0.0
Parsing documentation for cocoapods-search-1.0.0
Installing ri documentation for cocoapods-search-1.0.0
Parsing documentation for cocoapods-plugins-1.0.0
Installing ri documentation for cocoapods-plugins-1.0.0
Parsing documentation for cocoapods-downloader-1.0.1
Installing ri documentation for cocoapods-downloader-1.0.1
Parsing documentation for cocoapods-deintegrate-1.0.0
Installing ri documentation for cocoapods-deintegrate-1.0.0
Parsing documentation for fuzzy_match-2.0.4
Installing ri documentation for fuzzy_match-2.0.4
Parsing documentation for cocoapods-core-1.0.1
Installing ri documentation for cocoapods-core-1.0.1
Parsing documentation for cocoapods-1.0.1
Installing ri documentation for cocoapods-1.0.1
Done installing documentation for nap, fourflusher, escape, colored, concurrent-ruby, thread_safe, tzinfo, i18n, activesupport, claide, xcodeproj, molinillo, cocoapods-try, netrc, cocoapods-trunk, cocoapods-stats, cocoapods-search, cocoapods-plugins, cocoapods-downloader, cocoapods-deintegrate, fuzzy_match, cocoapods-core, cocoapods after 146 seconds
23 gems installed