title: IOS: write a string in a file txt from an array
body: <p>I have an array composed by other array:</p>
  
  <p>example my array with two arrays inside:</p>
  
  <p>myArray = [(element1, element2, element3)],[(element4,element5,element6)]
  this is only an example to show that myArray have two arrays (these elements are string)</p>
  
  <p>now I want write in a txt file these elements in this way:</p>
  
  <pre><code> element1#element2#element3;element4#element5#element6;
  </code></pre>
  
  <p>what is the code to create this string to write in txt file?</p>