今天新建个工程，执行pod install时出现如下一大串错误提示，查了查，原因是 xcode 版本和 cocoapods 版本不匹配，一般是先从的升级造成的，所以老工程 pod install 没问题，新工程有问题。解决办法就是升级 cocoapods，升级 cocoapods 时会遇到无法升级的问题，gem sources换成https://gems.ruby-china.com即可。
具体记录如下，可做参考：
### Report
* What did you do?
* What did you expect to happen?
* What happened instead?
### Stack
```
CocoaPods : 1.4.0.beta.2
Ruby : ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin15]
RubyGems : 2.5.1
Host : Mac OS X 10.13.2 (17C88)
Xcode : 9.4.1 (9F2000)
Git : git version 2.15.2 (Apple Git-101.1)
Ruby lib dir : /Users/liudonghao/.rvm/rubies/ruby-2.3.0/lib
Repositories : master - https://github.com/CocoaPods/Specs.git @ fd337daf50a57f544aa5d73a904c34a63c273ce3
```
### Plugins
```
cocoapods-deintegrate : 1.0.1
cocoapods-plugins : 1.0.0
cocoapods-search : 1.0.0
cocoapods-stats : 1.0.0
cocoapods-trunk : 1.3.0
cocoapods-try : 1.1.0
```
### Podfile
```ruby
platform :ios, '7.0'
target "RepairPlatform" do
pod 'SDWebImage', '3.7.2'
end
```
### Error
```
RuntimeError - [Xcodeproj] Unknown object version.
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/xcodeproj-1.5.3/lib/xcodeproj/project.rb:217:in `initialize_from_file'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/xcodeproj-1.5.3/lib/xcodeproj/project.rb:102:in `open'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/installer/analyzer.rb:907:in `block (2 levels) in inspect_targets_to_integrate'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/installer/analyzer.rb:906:in `each'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/installer/analyzer.rb:906:in `block in inspect_targets_to_integrate'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/user_interface.rb:64:in `section'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/installer/analyzer.rb:901:in `inspect_targets_to_integrate'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/installer/analyzer.rb:75:in `analyze'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/installer.rb:243:in `analyze'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/installer.rb:154:in `block in resolve_dependencies'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/user_interface.rb:64:in `section'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/installer.rb:153:in `resolve_dependencies'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/installer.rb:116:in `install!'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/command/install.rb:41:in `run'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/claide-1.0.2/lib/claide/command.rb:334:in `run'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/lib/cocoapods/command.rb:52:in `run'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/gems/cocoapods-1.4.0.beta.2/bin/pod:55:in `
/Users/liudonghao/.rvm/gems/ruby-2.3.0/bin/pod:23:in `load'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/bin/pod:23:in `
/Users/liudonghao/.rvm/gems/ruby-2.3.0/bin/ruby_executable_hooks:15:in `eval'
/Users/liudonghao/.rvm/gems/ruby-2.3.0/bin/ruby_executable_hooks:15:in `
```
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[!] Oh no, an error occurred.
Search for existing GitHub issues similar to yours:
https://github.com/CocoaPods/CocoaPods/search?q=%5BXcodeproj%5D+Unknown+object+version.&type=Issues
If none exists, create a ticket, with the template displayed above, on:
https://github.com/CocoaPods/CocoaPods/issues/new
Be sure to first read the contributing guide for details on how to properly submit a ticket:
https://github.com/CocoaPods/CocoaPods/blob/master/CONTRIBUTING.md
Don't forget to anonymize any private data!
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and 42 more at:
=======================
注意到：RuntimeError - [Xcodeproj] Unknown object version.
- 原因:`xcode`版本和现在`CocoaPods `的版本问题`不匹配`。- 解决方法: 更新`cocoaPods`的版本 ，在终端执行如下命令`sudo gem install cocoapods --pre`，然后在相对应`podfile`文件所在路径下执行`pod install `即可。
执行sudo gem install cocoapods --pre时又遇到错误，一般是因为
1.gem sources无法提供更新，把taobao Gems移除掉就好。
解决办法:gem sources --remove https://ruby.taobao.org/
gem sources --add https://gems.ruby-china.com
//再查看一下gem sources -l
然后就可以正常pod install了.
2.如果出现提示While executing gem ... (Gem::FilePermissionError)
You don't have write permissions for the /usr/bin directory.
表示没有权限读写/usr/bin
命令改成这样便可$ sudo gem install -n /usr/local/bin cocoapods --pre