很多公司项目，都习惯忽略Pods文件
现在的一些Demo也是如此，clone下来的项目还需要pod install下

可能会遇到如下问题

localhost:CYLTabBarController-master Shen$ pod install
Analyzing dependencies
[!] CocoaPods could not find compatible versions for pod "CYLTabBarController/Lottie":
  In Podfile:
    CYLTabBarController/Lottie (~> 1.28.1)

None of your spec sources contain a spec satisfying the dependency: `CYLTabBarController/Lottie (~> 1.28.1)`.

You have either:
 * out-of-date source repos which you can update with `pod repo update` or with `pod install --repo-update`.
 * mistyped the name or version.
 * not added the source repo that hosts the Podspec to your Podfile.

Note: as of CocoaPods 1.0, `pod repo update` does not happen on `pod install` by default.

[!] Automatically assigning platform `ios` with version `9.0` on target `CYLTabBarController` because no platform was specified. Please specify a platform for this target in your Podfile. See `https://guides.cocoapods.org/syntax/podfile.html#platform`.

虽然不知道具体原因，先按照提示的内容试一试
于是就执行了pod install --repo-update命令

localhost:CYLTabBarController-master Shen$ pod install --repo-update
Updating local specs repositories
  $ /usr/bin/git -C /Users/Shen/.cocoapods/repos/master fetch origin --progress
  remote: Enumerating objects: 128420, done.        
  remote: Counting objects: 100% (128420/128420), done.        
  remote: Compressing objects: 100% (4377/4377), done.        
  remote: Total 590430 (delta 125560), reused 126011 (delta 123745), pack-reused 462010        
  Receiving objects: 100% (590430/590430), 66.08 MiB | 141.00 KiB/s, done.
  Resolving deltas: 100% (372453/372453), completed with 29658 local objects.
  From https://github.com/CocoaPods/Specs
     89de7c94e0e..2cd6c7209ff  master      -> origin/master
   * [new branch]              cdn_scripts -> origin/cdn_scripts
   * [new branch]              indexes     -> origin/indexes
   * [new branch]              netlify     -> origin/netlify
  $ /usr/bin/git -C /Users/Shen/.cocoapods/repos/master rev-parse --abbrev-ref HEAD
  master
  $ /usr/bin/git -C /Users/Shen/.cocoapods/repos/master reset --hard origin/master
  Checking out files: 100% (52349/52349), done.
  HEAD is now at 2cd6c7209ff [Add] Peatio 0.5.1
warning: inexact rename detection was skipped due to too many files.
warning: you may want to set your diff.renameLimit variable to at least 50823 and retry the command.

CocoaPods 1.7.3 is available.
To update use: `sudo gem install cocoapods`

For more information, see https://blog.cocoapods.org and the CHANGELOG for this version at https://github.com/CocoaPods/CocoaPods/releases/tag/1.7.3

Analyzing dependencies
Downloading dependencies
Installing CYLTabBarController (1.28.1)
Installing MJRefresh (3.2.0)
Installing lottie-ios (2.5.3)
Generating Pods project
Integrating client project
Sending stats
Pod installation complete! There are 2 dependencies from the Podfile and 3 total pods installed.

[!] Automatically assigning platform `ios` with version `9.0` on target `CYLTabBarController` because no platform was specified. Please specify a platform for this target in your Podfile. See `https://guides.cocoapods.org/syntax/podfile.html#platform`.

看着log没啥问题，也都装上了，跑起来，直接报错了：

build失败

习惯性的搜了搜:
看的第一篇
看的第二篇

那就先检查下本地版本：

localhost:CYLTabBarController Shen$ pod --version
1.5.3

更新本地cocoapods:

localhost:CYLTabBarController Shen$ sudo gem install -n /usr/local/bin cocoapods --pre
Successfully installed xcodeproj-1.10.0
Fetching: fourflusher-2.3.1.gem (100%)
Successfully installed fourflusher-2.3.1
Fetching: ruby-macho-1.4.0.gem (100%)
Successfully installed ruby-macho-1.4.0
Fetching: cocoapods-1.7.3.gem (100%)
Successfully installed cocoapods-1.7.3
Parsing documentation for xcodeproj-1.10.0
Installing ri documentation for xcodeproj-1.10.0
Parsing documentation for fourflusher-2.3.1
Installing ri documentation for fourflusher-2.3.1
Parsing documentation for ruby-macho-1.4.0
Installing ri documentation for ruby-macho-1.4.0
Parsing documentation for cocoapods-1.7.3
Installing ri documentation for cocoapods-1.7.3
Done installing documentation for xcodeproj, fourflusher, ruby-macho, cocoapods after 7 seconds
4 gems installed
localhost:CYLTabBarController Shen$ pod --version
1.7.3

再install一次

localhost:CYLTabBarController Shen$ pod install
Analyzing dependencies
Downloading dependencies
Using CYLTabBarController (1.28.1)
Using MJRefresh (3.2.0)
Using lottie-ios (2.5.3)
Generating Pods project
Integrating client project
Sending stats
Pod installation complete! There are 2 dependencies from the Podfile and 3 total pods installed.

[!] Automatically assigning platform `ios` with version `9.0` on target `CYLTabBarController` because no platform was specified. Please specify a platform for this target in your Podfile. See `https://guides.cocoapods.org/syntax/podfile.html#platform`.

成功运行。