title: NSPredicate filter array with first character
body: <p>I'm trying to filter an array with the first letter of name </p>
  
  <p>I'm using this : </p>
  
  <pre><code>let predicate = NSPredicate(format: "name beginswith[c] %@", sections.objectAtIndex(section) as! String)
      let sectionArray = self.mContacts.filteredArrayUsingPredicate(predicate)
  </code></pre>
  
  <p>Where section is : </p>
  
  <pre><code>let sections = NSArray(objects: "#","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z")
  </code></pre>
  
  <p># must contain all the name begin by a digit. </p>
  
  <p>But I can not filter the name begin by digit with this method. </p>
  
  <p>I'm looking for some advices, thanks you</p>