title: map json response into nested typescript object with rxjs
body: <p>In my Angular2-App I´m receiving a JSON-Response via http-Request that kind of looks like that:</p>
  
  <pre><code>{
    "documents": [
      {
        "title": "Example-Doc 1",
        "versions": [
          {
            "fileSize": 15360
          },
          {
            "fileSize": 2048
          }
        ]
      },
      {
        "title": "Example-Doc 2",
        "versions": [
          {
            "fileSize": 15360
          },
          {
            "fileSize": 2048
          }
        ]
      }
    ],
    "meta": {
      "total": [2]
    }
  }
  </code></pre>
  
  <p>Now i wonder how to map this structure into my TypeScript-Classes, i checked different approaches, but it never worked. I actually need the constructor of the Version class to be called.</p>
  
  <pre><code>export class Document {
    title: string;        // Titel des Dokuments
    versions: Version[]; 
  }
  </code></pre>