title: How to convert NSString to NSArray with characters one by one in Objective-C
body: <p>I'd like to convert <code>NSString(ex. @"HELLO")</code> to <code>NSArray(ex. [@"H", @"E", @"L", @"L", @"O", nil])</code>.</p>
  
  <p>First, I tried to use <code>componentsSeparatedByString</code>. But it needs to indicate separator, so I could not.
  How can I do that?</p>