Typing Your Database

The core idea behind Typed Firestore is that you define typed collection references once, and all API functions infer their types from there.

Top-Level Collections

For top-level collections, cast the collection reference to a CollectionReference<T>:

export const refs = {
  users: db.collection("users") as CollectionReference<User>,
  books: db.collection("books") as CollectionReference<Book>,
} as const;

Sub-Collections

For sub-collections, use a function that returns the reference:

export const refs = {
  userWishlist: (userId: string) =>
    db
      .collection("users")
      .doc(userId)
      .collection("wishlist") as CollectionReference<WishlistItem>,
} as const;

Collection Groups

Collection groups are also supported:

const groupRef = db.collectionGroup(
  "wishlist",
) as CollectionGroup<WishlistItem>;

const allWishlistItems = await getDocuments(groupRef, (query) =>
  query.where("is_archived", "==", false),
);

Specific Documents

If you have collections with specific documents that have their own distinct types, you can declare the type for each individual document using a DocumentReference, and use the API that is focused on specific documents, like getSpecificDocument.

Where Typing Is Not Applied

The query where() function still uses the official Firestore API. No type-safety is provided there. This is a deliberate trade-off for simplicity and familiarity.

If you make a mistake in a where() clause, there is little chance of ruining data in the database, and you will likely discover the mistake during development.

Note that select statements are typed — see the Collections documentation for details.