title: isEqual to operator is not working properly in Flutter Firestore
body: <p>I'm trying to perform a compound query in Cloud Firestore with the <code>isEqualTo</code> operator in Flutter, inside a <code>StreamBuilder</code>, like this:</p>
  
  <pre><code>Firestore.instance
    .collection('produtos')
    .where("NProduto", isEqualTo: productClicked)
    .snapshots()
    .listen((data) =&gt;
    data.documents.forEach((doc) =&gt; nomeProdutoClicked = doc["Nome"]));
  </code></pre>
  
  <p>But when i try to use <code>forEach</code> in the last line, it never seems to add to a list, to set to a variable or anything like that, the only thing that worked was printing <code>(doc)</code>.
  I've tried doing it outside the StreamBuilder in a separate methos but I wasn't able to make it work in any way. 
  Essentially, what I'm trying to do is get a document from a different collection as that as the one I'm using in the StreamBuilder. </p>
  
  <p>If you know another way to do this, or know how to solve this issue, please help me. I will be eternally grateful hahhahah :)</p>