pod init 失败

报错信息

[!] Oh no, an error occurred.

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Looking for related issues on cocoapods/cocoapods...
 - Pod init. Unknown object version
   https://github.com/CocoaPods/CocoaPods/issues/7907 [closed] [2 comments]
   a week ago

 - RuntimeError - [Xcodeproj] Unknown object version.
   https://github.com/CocoaPods/CocoaPods/issues/7697 [closed] [27 comments]
   a day ago

 - Unknown object version
   https://github.com/CocoaPods/CocoaPods/issues/7760 [closed] [1 comment]
   21 May 2018

and 41 more at:
https://github.com/cocoapods/cocoapods/search?q=[Xcodeproj]%20Unknown%20object%20version.&type=Issues&utf8=✓

报错的大概意思是，CocoaPods版本与xcode版本不一样。
百度了一下解决方法。

gem install cocoapods --pre

更新下 CocoaPods 就可以了