title: Getting specific range of characters from a string swift 3
body: <p>i would like to get specific characters from my string, like this for example</p>
  
  <pre><code>var str = "hey steve @steve123, you would love this!"
  
  // Without doing this
  var theCharactersIWantFromTheString = "@steve123"
  </code></pre>
  
  <p>How would i just retrieve the @steve123 from str</p>