Thank you for the idea! :D

4. Install Cocoapods with gem

gem install cocoapods

3. Install Ruby with rbenv, and init rbenv in .zprofile

rbenv install -l (this will show a list of supported version)
rbenv install x.x.x (choose your prefered version)
rbenv global x.x.x

Then, add the following to .zprofile
export PATH="$HOME/.rbenv/bin:$PATH"
eval "$(rbenv init - zsh)"

2. Install rbenv with Homebrew, and init it

brew install rbenv
rbenv init

More details:

1. Install Homebrew - the command can be found in brew.sh

Thank you!

Thank you!

Thank you!

This problem cost me 200 yuan. Hard way to learn something....