使用命令
sudo gem install cocoapods安装 cocoapods时，报错：
ERROR: While executing gem ... (Gem::FilePermissionError)
You don't have write permissions for the /usr/bin directory.更换命令为：
sudo gem install -n /usr/local/bin cocoapods即可。
使用命令
sudo gem install cocoapods安装 cocoapods时，报错：
ERROR: While executing gem ... (Gem::FilePermissionError)
You don't have write permissions for the /usr/bin directory.更换命令为：
sudo gem install -n /usr/local/bin cocoapods即可。