title: JSONDecoder - Execute method for each element decoded
body: <p>I am using JSONDecoder to decode JSON to an array of MyModel : </p>
  
  <pre><code>myModelArray : [MyModel] = try JSONDecoder().decode([MyModel].self, from: data)
  </code></pre>
  
  <p>Everything is working fine, I get my array, but I want to execute a method for each element of my model array each time the element finished to be decoded. 
  Right now I am doing this : </p>
  
  <pre><code>for city in myModelArray! {
      //Creating polygon 
      city.createPolygon()
  }
  </code></pre>
  
  <p>It works but it is not optimal, is there a way to execute a method each time the Decoder finished to decode one element of the array ? Like a completition for example ? </p>
  
  <p>Thanks</p>