系统为mac os 10.11，command tool什么的都安装了
在执行bundle install时出现下面错误：
An error occurred while installing nokogiri (1.6.2.1), and Bundler cannot continue.
Make sure that `gem install nokogiri -v ‘1.6.2.1‘` succeeds before bundling.
往前翻了下，错误详细为：
Installing nokogiri 1.6.2.1 with native extensions Building nokogiri using packaged libraries. Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension. /usr/local/bin/ruby extconf.rb Building nokogiri using packaged libraries. ----- libiconv is missing. please visit http://nokogiri.org/tutorials/installing_nokogiri.html for help with installing dependencies. ----- *** extconf.rb failed *** Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. Check the mkmf.log file for more details. You may need configuration options. Provided configuration options: --with-opt-dir --without-opt-dir --with-opt-include --without-opt-include=${opt-dir}/include --with-opt-lib --without-opt-lib=${opt-dir}/lib --with-make-prog --without-make-prog --srcdir=. --curdir --ruby=/usr/local/bin/ruby --help --clean --use-system-libraries --enable-static --disable-static --with-zlib-dir --without-zlib-dir --with-zlib-include --without-zlib-include=${zlib-dir}/include --with-zlib-lib --without-zlib-lib=${zlib-dir}/lib --enable-cross-build --disable-cross-build Gem files will remain installed in /Users/sophia/ashelf/vendor/bundle/gems/nokogiri-1.6.2.1 for inspection. Results logged to /Users/sophia/ashelf/vendor/bundle/gems/nokogiri-1.6.2.1/ext/nokogiri/gem_make.out
里面有一句：“libiconv is missing. please visit http://nokogiri.org/tutorials/installing_nokogiri.html for help with installing dependencies.”
解决方法：
brew install libiconv
brew link libiconv
然后看到输出的链接地址为“/usr/local/Cellar/libiconv/1.14/”
执行命令：
gem install nokogiri -v ‘1.6.2.1‘ -- --with-iconv-dir=/usr/local/Cellar/libiconv/1.14/
上面这个命令每次执行都没有加 -v ‘1.6.2.1‘ ，所以一直装的1.6.7.2，导致bundle install总失败，好二啊/(ㄒoㄒ)/~~
An error occurred while installing nokogiri (1.6.2.1), and Bundler cannot continue.
原文：http://www.cnblogs.com/Sophiawow/p/5178820.html