Typesafe Firestore collection #firebase #firestore #typescript

firebase.ts

// A generic Firestore converter that provides type inference
export const genericConverter = <T>() => ({
	toFirestore: (data: PartialWithFieldValue<T>) => data ?? {},
	fromFirestore: (snap: QueryDocumentSnapshot) => snap.data() as T,
});

// A wrapper of collection() that uses a generic converter to provide type inference
export const typedCollection = <T>(db: Firestore, name: string) =>
	collection(db, name).withConverter<T>(genericConverter<T>());

// Example usage:
type User = { name: string; age: number };
onSnapshot(typedCollection<User>(db, 'users'), (snapshot) => {
	requests = snapshot.docs
		.map((doc) => doc.data())
		.map((doc) => ({
			text: doc.name,
			upvotes: doc.age,
		}));
});