title: replace characters in NSString
body: <p>I would like to wipe a NSString object in my code (replace every characters by 0).</p>
  
  <p>To do that I tried this :</p>
  
  <pre><code>NSString *myString;
  for (int i=0; i&lt;[myString length]; i++) 
  {
  myString[i] = 0;
  }
  </code></pre>
  
  <p>But it doesn't compile : "Incompatible types in assignment" at line <em>myString[i] = 0;</em></p>
  
  <p>I understand, but I can't use function <em>stringByReplacingOccurancesOfString</em> because it creates a new object and I would like to replace characters in my first object.</p>
  
  <p>Any help ?</p>