title: 'Embed Objects In' menu items are all disabled. How to enable?
body: <p>I'm following the instructions for creating a ScrollView in the book 'Cocoa Programming for Mac OS X, 3rd Edition'. I'm using Xcode 3.2.3.</p>
  
  <p>I've already created a view, into which I've drawn shapes and lines.</p>
  
  <p>The next task is to convert this to a NSScrollView, which according to the book should be a simple case of selecting the existing view and choosing Layout -> Embed Objects In -> Scroll View.</p>
  
  <p>However whatever object I select, the items in the 'Embed Objects In' menu are all disabled.</p>
  
  <p>How can I enable the Embed Objects In -> Scroll View item?</p>