After the upgrade macOS10.13.4, CocoaPods problems encountered (You do not have write permissions ...)

After the upgrade Xcode10, use a little problem CocoaPods encountered, make a note of
the input terminal upgrade instructions, display

 

ERROR:  While executing gem ... (Gem::FilePermissionError)

    You don't have write permissions for the /Library/Ruby/Gems/2.3.0 directory.
 

Solution:

$sudo gem update --system
$gem install -n /usr/local/bin sass