title: assign variable only if it is null
body: <p>on Ruby one have something like this:</p>
  
  <pre><code>@var ||= 'value' 
  </code></pre>
  
  <p>basically, it means that <code>@var</code> will be assigned <code>'value'</code> only if <code>@var</code> is not assigned yet (e.g. if <code>@var</code> is <code>nil</code>)</p>
  
  <p>I'm looking for the same on Kotlin, but so far, the closest thing would be the elvis operator. Is there something like that and I missed the documentation?</p>