升级Cocoapods 1.1.0

- 执行命令更新、查看版本

sudo gem update --system
sudo gem install cocoapods
pod setup

pod --version

输入命令sudo gem install cocoapods --pre 升级

此时会报错

hideOnBush:UAV_iOS Theshy$ sudo gem install cocoapods --pre
Fetching: cocoapods-core-1.1.0.beta.2.gem (100%)
Successfully installed cocoapods-core-1.1.0.beta.2
Fetching: cocoapods-deintegrate-1.0.1.gem (100%)
Successfully installed cocoapods-deintegrate-1.0.1
Fetching: cocoapods-downloader-1.1.1.gem (100%)
Successfully installed cocoapods-downloader-1.1.1
Fetching: cocoapods-try-1.1.0.gem (100%)
Successfully installed cocoapods-try-1.1.0
Fetching: molinillo-0.5.0.gem (100%)
Successfully installed molinillo-0.5.0
Fetching: xcodeproj-1.3.0.gem (100%)
ERROR:  While executing gem ... (Errno::EPERM)
    Operation not permitted - /usr/bin/xcodeproj
hideOnBush:UAV_iOS Theshy$ sudo gem install cocoapods --pre /usr/local/bin cocoapods
ERROR:  While executing gem ... (Errno::EPERM)
    Operation not permitted - /usr/bin/xcodeproj

原因

Cocoapods在10.11系统上发生了变化
stack overflow上的解释是这样的
This is happening because Apple has enabled rootless on the new install
也就是说在10.11系统上苹果已经启用无根的安装

在这种情况下，如果你使用如下的命令：
sudo gem install cocoa pods
就会出现这样的提示：

ERROR:  While executing gem ... (Errno::EPERM) Operation not permitted - /usr/bin/pod

此时我们输入命令

sudo gem install cocoapods --pre -n /usr/local/bin cocoa pods

就能正确升级成功

降级cocopods

执行sudo gem uninstall cocoapods 卸载现有 cocopods
安装

sudo gem install cocoapods -v 0.39.0 

若是报错

ERROR:  While executing gem ... (Errno::EPERM)
    Operation not permitted - /usr/bin/pod

执行命令sudo gem install cocoapods -v 0.39.0 -n /usr/local/bin
则下载成功 0.39版本

参考：
http://www.cnblogs.com/lear/p/5208816.html