title: NSSortDescriptor in Swift - sort by days left to next birthday
body: <p>I'm working on my first swift app. It's a simple Birthday list which stores Birthdays to CoreData with name, date of birth (as NSDate) and shows them in a table-view.</p>
  
  <p>Now what I try doing is sorting that table-view by days-left to the next Birthday.</p>
  
  <p>I already show "days-left" in the table view cell by calculating the next Birthday and the "days-left" every time I load the table-view - like this:</p>
  
  <pre><code>    let diffDateComponents = NSCalendar.currentCalendar().components([NSCalendarUnit.Day], fromDate: NSDate(), toDate: nextBirthDay, options: NSCalendarOptions.init(rawValue: 0))
  </code></pre>
  
  <p>How can I now sort the table-view by diffDateComponents?</p>