更新cocoapods

/* Mac OS 10.11, some cocoapods commands to change. 
If you have a pod setup or pod update problem, and it is difficult to solve, I suggest 10.11. 
Uninstall reinstall after installation of cocoapods has some different commands, the following summary:*/

// check the ruby environment, if necessary, please update as follows
$ sudo gem update --system
 
// uninstall cocoapods
$ sudo gem uninstall cocoapods
 
// reinstall cocoapods (Setup command has changed)
$ sudo gem install cocoapods // Before 10.11
$ sudo gem install -n /usr/local/bin cocoa pods // After 10.11
  
$ sudo chmod +rx /usr/local/bin
$ sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer

// taking CocoaPods Specs repository copy to your computer under directory ~/.cocoapods
pod setup

来源：https://stackoverflow.com/a/50959034/2481602

git clone https://github.com/CocoaPods/Specs  ~/.cocoapods/repos/master