1、查看ruby是否安装，一般需要再更新下
$ruby -v
ruby 2.0.0p648 (2015-12-16 revision 53162) [universal.x86_64-darwin16]
$sudo gem update --system
2、更新ruby镜像
淘宝的那个镜像(https://ruby.taobao.org/ )已经不可用了。官方的需要FQ。所以我们现在用最新支持的ruby镜像(https://gems.ruby-china.org/)
$gem sources --remove https://rubygems.org/
$gem sources --add https://gems.ruby-china.org/
$gem sources -l （用来检查使用替换镜像位置成功）
3、安装
$sudo gem install -n /usr/local/bin cocoapods --pre
出现如下，说明成功
Successfully installed xcodeproj-1.4.4
Fetching: ruby-macho-1.1.0.gem (100%)
Successfully installed ruby-macho-1.1.0
Fetching: nap-1.1.0.gem (100%)
Successfully installed nap-1.1.0
Fetching: molinillo-0.5.7.gem (100%)
Successfully installed molinillo-0.5.7
Fetching: gh_inspector-1.0.3.gem (100%)
Successfully installed gh_inspector-1.0.3
Fetching: fourflusher-2.0.1.gem (100%)
Successfully installed fourflusher-2.0.1
Fetching: escape-0.0.4.gem (100%)
Successfully installed escape-0.0.4
Fetching: cocoapods-try-1.1.0.gem (100%)
Successfully installed cocoapods-try-1.1.0
Fetching: netrc-0.7.8.gem (100%)
Successfully installed netrc-0.7.8
Fetching: cocoapods-trunk-1.2.0.gem (100%)
Successfully installed cocoapods-trunk-1.2.0
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-1.1.3.gem (100%)
Successfully installed cocoapods-downloader-1.1.3
Fetching: cocoapods-deintegrate-1.0.1.gem (100%)
Successfully installed cocoapods-deintegrate-1.0.1
Fetching: fuzzy_match-2.0.4.gem (100%)
Successfully installed fuzzy_match-2.0.4
Fetching: thread_safe-0.3.6.gem (100%)
Successfully installed thread_safe-0.3.6
Fetching: tzinfo-1.2.3.gem (100%)
Successfully installed tzinfo-1.2.3
Fetching: minitest-5.10.2.gem (100%)
Successfully installed minitest-5.10.2
Fetching: i18n-0.8.1.gem (100%)
Successfully installed i18n-0.8.1
Fetching: activesupport-4.2.8.gem (100%)
Successfully installed activesupport-4.2.8
Fetching: cocoapods-core-1.2.1.gem (100%)
Successfully installed cocoapods-core-1.2.1
Fetching: cocoapods-1.2.1.gem (100%)
Successfully installed cocoapods-1.2.1
Parsing documentation for xcodeproj-1.4.4
Installing ri documentation for xcodeproj-1.4.4
Parsing documentation for ruby-macho-1.1.0
Installing ri documentation for ruby-macho-1.1.0
Parsing documentation for nap-1.1.0
Installing ri documentation for nap-1.1.0
Parsing documentation for molinillo-0.5.7
Installing ri documentation for molinillo-0.5.7
Parsing documentation for gh_inspector-1.0.3
Installing ri documentation for gh_inspector-1.0.3
Parsing documentation for fourflusher-2.0.1
Installing ri documentation for fourflusher-2.0.1
Parsing documentation for escape-0.0.4
Installing ri documentation for escape-0.0.4
Parsing documentation for cocoapods-try-1.1.0
Installing ri documentation for cocoapods-try-1.1.0
Parsing documentation for netrc-0.7.8
Installing ri documentation for netrc-0.7.8
Parsing documentation for cocoapods-trunk-1.2.0
Installing ri documentation for cocoapods-trunk-1.2.0
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-1.1.3
Installing ri documentation for cocoapods-downloader-1.1.3
Parsing documentation for cocoapods-deintegrate-1.0.1
Installing ri documentation for cocoapods-deintegrate-1.0.1
Parsing documentation for fuzzy_match-2.0.4
Installing ri documentation for fuzzy_match-2.0.4
Parsing documentation for thread_safe-0.3.6
Installing ri documentation for thread_safe-0.3.6
Parsing documentation for tzinfo-1.2.3
Installing ri documentation for tzinfo-1.2.3
Parsing documentation for minitest-5.10.2
Installing ri documentation for minitest-5.10.2
Parsing documentation for i18n-0.8.1
Installing ri documentation for i18n-0.8.1
Parsing documentation for activesupport-4.2.8
unable to convert "\x84" from ASCII-8BIT to UTF-8 for lib/active_support/values/unicode_tables.dat, skipping
Installing ri documentation for activesupport-4.2.8
Parsing documentation for cocoapods-core-1.2.1
Installing ri documentation for cocoapods-core-1.2.1
Parsing documentation for cocoapods-1.2.1
Installing ri documentation for cocoapods-1.2.1
23 gems installed