PROMPT> gem uninstall cocoapods

Select gem to uninstall:
 1. cocoapods-0.32.1
 2. cocoapods-0.33.1
 3. cocoapods-0.36.0.beta.2
 4. cocoapods-0.38.2
 5. cocoapods-0.39.0
 6. cocoapods-1.0.0
 7. All versions
> 6
Successfully uninstalled cocoapods-1.0.0
PROMPT> gem install cocoapods -v 0.39.0
Successfully installed cocoapods-0.39.0
Parsing documentation for cocoapods-0.39.0
Done installing documentation for cocoapods after 1 seconds
1 gem installed
PROMPT> pod --version
0.39.0
PROMPT>

PROMPT> gem uninstall cocoapods

Select gem to uninstall:
 1. cocoapods-0.32.1
 2. cocoapods-0.33.1
 3. cocoapods-0.36.0.beta.2
 4. cocoapods-0.38.2
 5. cocoapods-0.39.0
 6. cocoapods-1.0.0
 7. All versions
> 6
Successfully uninstalled cocoapods-1.0.0
PROMPT> gem install cocoapods -v 0.39.0
Successfully installed cocoapods-0.39.0
Parsing documentation for cocoapods-0.39.0
Done installing documentation for cocoapods after 1 seconds
1 gem installed
PROMPT> pod --version
0.39.0
PROMPT>

如果您需要安装旧版本(例如0.25):

pod _0.25.0_ install

实际上，你不需要降级-如果你需要在一些项目中使用旧版本，只需要在pod命令后指定你需要使用的版本。

pod _0.37.2_ setup

在某些情况下，需要在主目录中删除一些隐藏的工件，以便up或降级生效:

rm -rf ~/.cocoapods

在我的情况下，我不得不从自制程序卸载

brew uninstall cocoapods