Flutter: Update specific index in list (Firestore)

Question

How exactly do you update a specific value in a list based on it's index? For example, in the following list:

0 [
    {
      first_name: name0,
      last_name: lastName0,
    }
  ]
1 [
    {
      first_name: name1,
      last_name: lastName1,
    }
  ]          

How can I update only "lastName1"? At the moment, I'm using a bit of a hacky solution using ArrayUnion, which uses data comparison instead of the actual index (I load the values into a form, delete the original value and then re-add it again):

 // Retrieve data at index, load into form

// Remove that index from List 
await Firestore.instance.collection(col).document(doc).updateData({
  'people': FieldValue.arrayRemove([person])
});

// Make changes to data via form

// Save back to list
 await Firestore.instance.collection(col).document(doc).updateData({
  'people': FieldValue.arrayUnion([person])
});

Is there a function that will allow me to specify which specific index's data to update? Something like (but using a List, not Map):

 await Firestore.instance.collection(col).document(doc).updateData({
  'people.$index.lastName1': 'newName')
 });

Answer 1

Waitting for answers