title: How to add variable to url. iOS
body: <p>I have a problem with adding my variable to url. 
  In code I have this:</p>
  
  <pre><code>self.imgURL = "https://openweathermap.org/img/w/\(self.dodatek).png"
  </code></pre>
  
  <p>and this doesn't work. In debugger it shows me this: </p>
  
  <pre><code>url String  "https://openweathermap.org/img/w/Optional(\50n\).png"  
  </code></pre>
  
  <p>but it should be like this: </p>
  
  <pre><code>https://openweathermap.org/img/w/50n.png
  </code></pre>
  
  <p>When I change my code to this: </p>
  
  <pre><code>self.imgURL = "https://openweathermap.org/img/w/50n.png"
  </code></pre>
  
  <p>it works, and shows me weather icon,but I want to put there my variable that takes icon name from json. </p>