title: append in middle of NSString in iPhone programming
body: <p>how to append the value of string in between NSString?</p>
  
  <p>for example:</p>
  
  <pre><code>NSString* str1 = @"Hello";
  
  NSString* str2 = @"Hi.."/*add contents of str1*/@"how r u??";
  </code></pre>
  
  <p>please tell me how to achieve this?? </p>