Add new field in nested object firestore Android

Question

On the Firestore documentation there is code to update the nested object field but there is no code or documentation about how we can add the new field in the nested object?

// Assume the document contains:
// {
//   name: "Frank",
//   favorites: { food: "Pizza", color: "Blue", subject: "recess" }
//   age: 12
// }
//
// To update age and favorite color:
db.collection("users").document("frank")
        .update(
                "age", 13,
                "favorites.color", "Red"
        );

As you can see here we are updating the favorites.color to Red, but how we can add the new field code in the favorites object?

Suppose I want to update the above document as the follows:

{
  name: "Frank",
  favorites: { food: "Pizza", color: "Blue", subject: "recess", code:32 }
  age: 12
}

Answer 1

If the document does exist, its contents will not be overwritten with the newly provided data if you specify that the data should be merged into the existing document like this:

Map<String, Object> favorites = new HashMap<>();
Map<String, Object> favorite = new HashMap<>();
favorite.put("code", 32);
favorites.put("favorites", favorite);
rootRef.collection("users").document("frank").set(favorites, SetOptions.merge());