title: How do update array values in Flutter cloud_firestore?
body: <p>I have a document with an array field in it.</p>
  
  <p>How can I update the array?</p>
  
  <p>In firebase functions, with typescript, I did something like this:</p>
  
  <pre><code>admin.firestore()
      .collection('friendships')
      .doc(caller.data["uid"])
      .update({
          friends: admin.firestore.FieldValue
              .arrayUnion({
                            friendDisplayName: snapshot.data["friendDisplayName"],
                            friendUid: snapshot.ref
                         })
      })
  </code></pre>
  
  <p>I cannot find any alternative with Flutter.. how can I do?</p>