主要步骤是更新cocoapods版本和修改gem源，然后可能会对gem进行更新
1、查看cocoapods版本
pod --version
2、更新cocoapods
sudo gem install -n /usr/local/bin cocoapods
3、查看gem版本
gem --version
gem -v
4、更新gem（可跳过）
sudo gem update --system
直接使用gem update --system命令会遇到目录权限不够的问题，报错如下
ERROR: While executing gem ... (Gem::FilePermissionError)
You don't have write permissions for the /Library/Ruby/Gems/2.3.0 directory.
直接使用sudo gem update --system命令也会遇到目录权限不够的问题，报错如下
ERROR: While executing gem ... (Gem::FilePermissionError)
You don't have write permissions for the /usr/bin directory.
修改文件权限之后仍然报错
sudo chmod 777 /Library/Ruby/Gems/2.3.0
gem update --system
ERROR: While executing gem ... (Errno::EACCES)
Permission denied @ rb_sysopen - /Library/Ruby/Gems/2.3.0/gems/rubygems-update-2.7.7/.autotest
博主一直未更新成功，之后发现用2.7.6版本也可以走下去，遂跳过。
5、修改gem源
进行gem更新和cocoapods更新时会遇到404错误，这是因为gem源不对所致，需要更改gem源，最开始是用的淘宝的源，后来换为中国镜像.org源，现在的源是中国镜像的.com源。可点击官网查看
gem源更改公告.jpg
更新gem报404错误和更新cocoapods报404错误提示
ERROR: While executing gem ... (Gem::RemoteFetcher::FetchError)
bad response Not Found 404 (https://gems.ruby-china.org/specs.4.8.gz)
ERROR: Could not find a valid gem 'cocoapods' (>= 0), here is why:
Unable to download data from https://gems.ruby-china.org/ - bad response Not Found 404 (https://gems.ruby-china.org/specs.4.8.gz)
修改gem源命令
gem sources --add https://gems.ruby-china.com/ --remove https://gems.ruby-china.org/
查看gem源命令
gem sources -l
