title: Ruby Uninitialized Constant NameError for Class Name
body: <p>I want to inherit a sub-class from a parent-class.</p>
  
  <p>Here is my code. 3 classes are created in 3 separate files.</p>
  
  <pre><code>class Transportation
  #codes
  end
  
  class Plane &lt; Transportation
  #codes
  end
  
  class Boat &lt; Transportation
  #codes
  end
  </code></pre>
  
  <p>And when I was running this code, I got the error for Boat, but no issue for Plane when I only have Plane created:</p>
  
  <pre><code>uninitialized constant Transportation (NameError)
  </code></pre>
  
  <p>Can anyone help me with this issue?</p>
  
  <p>Thanks</p>