废话不多说、直接解释

在下载某个ios源码后，我们需要在控制器进入目录之后执行pod install：

$ pod install
然而会报错、如下

[!] Unable to find a specification for CrabCrashReporter

因此我们需要更新cocoapods，执行下面的命令，但是并没有更新成功。
`$ gem update cocoapod`
> `Updating installed gems Nothing to update`

查看当前版本：

`$ pod --version`
> `1.0.1`

怀疑source地址有变化：

`$ gem sources `
>```-l*** CURRENT SOURCES *** 
http://ruby.taobao.org/```

网上查看，告知taobao服务器已经改为https协议，因此执行如下：

`$ gem sources`
>``` -r http://ruby.taobao.org/http://ruby.taobao.org/ removed from sources $ gem sources -a https://ruby.taobao.org/https://ruby.taobao.org/ added to sources```

更新系统，提示没有权限：
$ gem update --system Updating rubygems-updateFetching: rubygems-update-2.5.1.gem (100%)ERROR: While executing gem ... (Gem::FilePermissionError) You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.
使用sudo来执行操作：

`$ sudo gem update --system`
> `Updating rubygems-updateFetching: rubygems-update-2.5.1.gem (100%)Successfully installed rubygems-update-2.5.1 Parsing documentation for rubygems-update-2.5.1`

执行安装:

`$ pod setup`
>`Setting up CocoaPods master repoSetup completed [!] CocoaPods was not able to update the `master `repo. `
`If this is an unexpected issue and persists you can inspect it running  `pod repo update --verbos ` `

根据提示执行repo更新:

`$ pod repo update --verbose `
> `Updating spec repo `master` $ /usr/bin/git pull --ff-only From https://github.com/CocoaPods/Specs a0baa68..9a14a05 master -> origin/master error: Your local changes to the following files would be overwritten by merge: CocoaPods-version.yml Specs/1PasswordExtension/1.0.0/1PasswordExtension.podspec.json Specs/1PasswordExtension/1.0.1/1PasswordExtension.podspec.json Specs/AKUTestKit/1.1.2/AKUTestKit.podspec.json Specs/ALCore Aborting Updating a5c6b67..9a14a05 [!] CocoaPods was not able to update the `master` repo. If this is an unexpected issue and persists you can inspect it running `pod repo update --verbose``

master分支还是失败，查看网上建议，先清除缓存

`rm -rf ~/.cocoapods/repos/master`
再重新运行：

`$ pod setup`
> `Setting up CocoaPods master repo CocoaPods 1.0.0.beta.2 is available.To update use: `gem install cocoapods --pre`[!] This is a test version we'd love you to try. For more information see http://blog.cocoapods.organd the CHANGELOG for this version http://git.io/BaH8pQ. Setup completed`

`$ gem install cocoapods`
> `........Installing ri documentation for cocoapods-1.1.1
Done installing documentation for gh_inspector, fourflusher, activesupport, claide, xcodeproj, molinillo, cocoapods-trunk, cocoapods-downloader, cocoapods-deintegrate, cocoapods-core, cocoapods after 15 seconds
11 gems installed`

最后，到下载的ios工程目录下，执行：
 `$  pod --version`
> `1.1.1`

`$ pod install`
> `Updating local specs repositories CocoaPods 1.0.0.beta.2 is available.To update use: `gem install cocoapods --pre`[!] 
This is a test version we'd love you to try. For more information see http://blog.cocoapods.organd the CHANGELOG for this version http://git.io/BaH8pQ. Analyzing dependenciesDownloading dependenciesInstalling AFNetworking (2.6.3)Installing AFOnoResponseSerializer (1.0.0)Installing DTCoreText (1.6.17)`

可见现在问题解决了！