I was trying run gem install json and got the following error
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
/System/Library/Framewo
To address the issue you can install the most recent version of ruby as described by @Sash. You can use the following commands to do so. In case you already have installed rvm, you don't need to reinstall it.
#Install rvm
\curl -sSL https://get.rvm.io | bash -s stable
#Install ruby version 2.0.0-p451
rvm install ruby-2.0.0-p451
#Print ruby version to verify that it was installed successfully
ruby -v
#Install json gem
sudo gem install json