title: Filtering 'string' values of elements in array in Swift
body: <p>As I am just starting my adventure with programming in general and with Swift in particular I am unable to solve my problem with filtering an array.</p>
  
  <p>While working with my book, I got to a chapter where arrays are explained and
  I had no problem with working with arrays untill now. Here is a code from my student's book :</p>
  
  <pre><code>var city = ["Boston", "London", "Chicago", "Atlanta"]
  let filtered = city.filter{$0.range(of:"o") != nil}
  </code></pre>
  
  <p>This is supposed to filter the cities with the letter "o" in it but when compiled this message is being shown :</p>
  
  <pre><code>error: value of type 'String' has no member 'range
  </code></pre>
  
  <p>So does it mean that I can't use <code>.range</code> for string values?
  What chould the code look like then?
  I am using ubuntu as my OS.</p>
  
  <p>Thanks in advance.</p>