Cocoapod gem错误

ArgumentError - Malformed version number string 

ERROR: While executing gem ... (Gem::FilePermissionError) You don't have write permissions for the /usr/bin directory.

gem 2.7.7 不支持 cocoapods 1.3.x . 1.4.x

要按照 rubygem in 2.7.6

或者cocoapods升级到1.5.3

看版本

gem -v 

 如何降到2.7.6

sudo gem install -n /usr/local/bin rubygems-update -v 2.7.6

sudo gem update -n /usr/local/bin --system 2.7.6

然后 pod install 就好了