title: NSString hasPrefix: function with case sensitivity
body: <p>Simple and may asked many time but little trick with this. We know, NSString doesn't work with case sensitivity for hasPrefix: method.</p>
  
  <pre><code>NSString *string = @"Xyzabcdedfghij";
      NSString *substring = @"xyz";
      if ([string hasPrefix:substring])
          NSLog(@"string has prefix "); // won't get here.
  </code></pre>
  
  <p><code>Question is:</code> <strong>Is there any built-in method for resolve this issue? I mean, <code>hasPrefix:</code> with case sensitive?</strong></p>
  
  <p>I could use below answer at least case. But want to know if there is any method which better than this..? </p>
  
  <p><strong>Known answer:</strong>(lease case)</p>
  
  <pre><code>if ([[test substringWithRange:NSMakeRange(0,3)] caseInsensitiveCompare:@"xyz"] == NSOrderedSame) {
       // ....
  }
  </code></pre>