【CocoaPods】ERROR: While executing gem ... Gem::DependencyError

今天安装 CocoaPods 时遇到了这个问题。

ERROR:  While executing gem ... (Gem::DependencyError)
    Unable to resolve dependencies: cocoapods requires cocoapods-trunk (< 2.0, >= 1.2.0), molinillo (~> 0.5.7), xcodeproj (< 2.0, >= 1.4.4), colored2 (~> 3.1), ruby-macho (~> 1.1)

解决方法：
用命令行把上面那些需要安装的东西挨个安装，最后再输入命令：

sudo gem install -n /usr/local/bin cocoapods

参考文章：
http://www.cnblogs.com/chuange-Strongload/p/5891903.html