RuntimeError - [Xcodeproj] Unkno

pod install 报错: RuntimeError - [Xcodeproj] Unknown object version.

➜  LBDemo git:(master) ✗ pod install
Analyzing dependencies

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### Command

```
/Users/yangda/.rvm/rubies/ruby-2.2.2/bin/pod install
```

### Report

* What did you do?

* What did you expect to happen?

* What happened instead?


### Stack

```
   CocoaPods : 1.2.1
        Ruby : ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]
    RubyGems : 2.7.7
        Host : Mac OS X 10.13.6 (17G65)
       Xcode : 9.4.1 (9F2000)
         Git : git version 2.10.0
Ruby lib dir : /Users/yangda/.rvm/rubies/ruby-2.2.2/lib
Repositories : edu-git-cocoapods-specs - https://mirrors.tuna.tsinghua.edu.cn/git/CocoaPods/Specs.git @ 62c6c4f83286ae8313f3d2183c00689663c327fa
               master - https://github.com/CocoaPods/Specs.git @ 62c6c4f83286ae8313f3d2183c00689663c327fa
```

### Plugins

```
cocoapods-deintegrate : 1.0.1
cocoapods-playgrounds : 1.2.2
cocoapods-plugins     : 1.0.0
cocoapods-search      : 1.0.0
cocoapods-stats       : 1.0.0
cocoapods-trunk       : 1.2.0
cocoapods-try         : 1.1.0
```

### Podfile

```ruby
source 'https://mirrors.tuna.tsinghua.edu.cn/git/CocoaPods/Specs.git'
platform :ios, '9.0'
target 'LBDemo' do
    pod 'AFNetworking'
    pod 'Masonry'
        pod 'SDWebImage', '~> 4.3.3'
end
```

### Error

```
RuntimeError - [Xcodeproj] Unknown object version.
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/xcodeproj-1.4.4/lib/xcodeproj/project.rb:217:in `initialize_from_file'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/xcodeproj-1.4.4/lib/xcodeproj/project.rb:102:in `open'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/installer/analyzer.rb:874:in `block (2 levels) in inspect_targets_to_integrate'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/installer/analyzer.rb:873:in `each'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/installer/analyzer.rb:873:in `block in inspect_targets_to_integrate'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/user_interface.rb:64:in `section'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/installer/analyzer.rb:868:in `inspect_targets_to_integrate'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/installer/analyzer.rb:66:in `analyze'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/installer.rb:236:in `analyze'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/installer.rb:150:in `block in resolve_dependencies'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/user_interface.rb:64:in `section'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/installer.rb:149:in `resolve_dependencies'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/installer.rb:110:in `install!'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/command/install.rb:41:in `run'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/claide-1.0.1/lib/claide/command.rb:334:in `run'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/lib/cocoapods/command.rb:52:in `run'
/Users/yangda/.rvm/gems/ruby-2.2.2@global/gems/cocoapods-1.2.1/bin/pod:55:in `<top (required)>'
/Users/yangda/.rvm/rubies/ruby-2.2.2/bin/pod:23:in `load'
/Users/yangda/.rvm/rubies/ruby-2.2.2/bin/pod:23:in `<main>'
```

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[!] Oh no, an error occurred.

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其实就是版本不匹配,大部分情况下升级pod就可以了:
gem install cocoapods --pre