title: How to split string into substrings on iOS?
body: <p>I received an <code>NSString</code> from the server. Now I want to split it into the substring which I need.
  How to split the string? </p>
  
  <p>For example: </p>
  
  <p>substring1:read from the second character to 5th character</p>
  
  <p>substring2:read 10 characters from the 6th character.</p>