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FirestoreDataConverter interface

Converter used by withConverter() to transform user objects of type T into Firestore data.

Using the converter allows you to specify generic type arguments when storing and retrieving objects from Firestore.

Signature:

export declare interface FirestoreDataConverter<T> 

Example

class Post {
  constructor(readonly title: string, readonly author: string) {}

  toString(): string {
    return this.title + ', by ' + this.author;
  }
}

const postConverter = {
  toFirestore(post: Post): firebase.firestore.DocumentData {
    return {title: post.title, author: post.author};
  },
  fromFirestore(
    snapshot: firebase.firestore.QueryDocumentSnapshot,
    options: firebase.firestore.SnapshotOptions
  ): Post {
    const data = snapshot.data(options)!;
    return new Post(data.title, data.author);
  }
};

const postSnap = await firebase.firestore()
  .collection('posts')
  .withConverter(postConverter)
  .doc().get();
const post = postSnap.data();
if (post !== undefined) {
  post.title; // string
  post.toString(); // Should be defined
  post.someNonExistentProperty; // TS error
}

Methods

Method	Description
fromFirestore(snapshot, options)	Called by the Firestore SDK to convert Firestore data into an object of type T. You can access your data by calling: snapshot.data(options).
toFirestore(modelObject)	Called by the Firestore SDK to convert a custom model object of type T into a plain JavaScript object (suitable for writing directly to the Firestore database). To use set() with merge and mergeFields, toFirestore() must be defined with Partial<T>.
toFirestore(modelObject, options)	Called by the Firestore SDK to convert a custom model object of type T into a plain JavaScript object (suitable for writing directly to the Firestore database). Used with setDoc(), and with merge:true or mergeFields.