title: How can I install Ruby on Rails 3 on OSX?
body: <p>I got a White Macbook and I have to go to a conference in 10 hours but I'm having a lot of problems.</p>
  
  <p>First, I wanted to have Rails 3, so I used MacPorts to install Ruby 1.8.7. It worked well ;) 
  Then I was thinking I should install Rails 3, but no, no!  It says:</p>
  
  <blockquote>
  <pre><code>$ sudo gem install rails --pre
  
  ERROR: Error installing rails:
  
  
              activesupport requires Ruby version &gt;= 1.8.7.
  </code></pre>
  </blockquote>
  
  <p>What should I do?  I already have 1.8.7!</p>