CODEWITHSUNDEEP
reactjsfirebasegoogle-cloud-platformgoogle-cloud-firestore
Justin
Justin

Reputation: 101

How to get document after set method in firestore while updating

I am making an update to my document. I use the set method because I want to overwrite my fields. Therefore, when i do my set, it works perfectly, modifying the object in the firestore database. But i am not able to return the document afterward. The error I get:

Cannot read property 'exists' of undefined
    at Firebase.js:127

Here is my code:

const updateItemFromCollection = async (collectionName, uid, data) => {
  return database
    .collection(collectionName)
    .doc(uid)
    .set(data, { merge: true })
    .then(doc => {
      if (!doc.exists) {
        console.log("No such document!"); //Error
      } else {
        return doc.data();
      }
    })
    .catch(error => {
      console.log(error);
    });
};

Upvotes: 1

Views: 2025

Answers (1)

Renaud Tarnec
Renaud Tarnec

Reputation: 83093

This is because the set() method returns a Promise<void> and not a Promise<DocumentSnapshot<T>>.

You will need to read the document again, as follows:

const updateItemFromCollection = async (collectionName, uid, data) => {

  const docRef = database.collection(collectionName).doc(uid);

  return docRef.set(data, { merge: true })
    .then(() => {
        return docRef.get();
    .then(doc => {
      if (!doc.exists) {
        console.log("No such document!"); //Error
      } else {
        return doc.data();
      }
    })
    .catch(error => {
      console.log(error);
    });
};

This is the way Firestore works, and AFAIK, it is based on the fact that you already know the value of the document fields, since you passed a corresponding object to set(). One could remark however that this is not true for the values calculated in the back-end based on sentinel values, see FieldValue.

Upvotes: 3

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