首先使用homebrew安装ruby：
$ brew install ruby
设置环境并应用
$ echo 'export PATH="/usr/local/opt/ruby/bin:$PATH"' >> /Users/xxx/.bash_profile
$ echo 'export LDFLAGS="-L/usr/local/opt/ruby/lib"' >> ~/.bash_profile
$ echo 'export CPPFLAGS="-I/usr/local/opt/ruby/include"' >> ~/.bash_profile
$ source ~/.bash_profile
检查环境
$ ruby -v
ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x86_64-darwin18]
$ which ruby
/usr/local/opt/ruby/bin/ruby
安装cocoapods
$ sudo gem install -n /usr/local/bin cocoapods
