title: How to insert NSString * between two NSString *
body: <p>I want to ask an NSString * question. I have a NSString * object. The content is like the following example. (like the CSV file)</p>
  
  <p>Example: (my file is longer than this one so much)</p>
  
  <pre><code>First Name,Last Name,Middle Name,Phone,Chan,Tim,Man,123-456-789,Tom,,,987-654-321
  </code></pre>
  
  <p>(if it is empty, no space between the ',')</p>
  
  <p>How can I insert the "(null)" NSString * / or NSString * object between the two ',' by using the objective C? </p>
  
  <pre><code>// After convent
  
  First Name,Last Name,Middle Name,Phone,Chan,Tim,Man,123-456-789,Tom,(null),(null),987-654-321
  </code></pre>
  
  <p>Thank you very much.</p>