CODEWITHSUNDEEP
flutterfirebasegoogle-cloud-firestore
Juan Real
Juan Real

Reputation: 1

How to update a firebase document field based on a value from another document in other collection? Flutter

I have a number in the usersnumber collection (counter document), and I want to take that number and put it in the users collection in the number field (as you can see in the photo). Is there any way I can get the data from usersnumber and update the users > collection > document > number?

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I expect having the number 10 from the usersnumber collection in the collection users > document > number: 0

Upvotes: 0

Views: 531

Answers (1)

Ronnie Smith
Ronnie Smith

Reputation: 18585

a transaction is a set of read and write operations on one or more documents.

Using the Cloud Firestore client libraries, you can group multiple operations into a single transaction. Transactions are useful when you want to update a field's value based on its current value, or the value of some other field.

https://firebase.google.com/docs/firestore/manage-data/transactions#transactions

import { runTransaction } from "firebase/firestore";

try {
  await runTransaction(db, async (transaction) => {
    const sfDoc = await transaction.get(sfDocRef);
    if (!sfDoc.exists()) {
      throw "Document does not exist!";
    }

    const newPopulation = sfDoc.data().population + 1;
    transaction.update(sfDocRef, { population: newPopulation });
  });
  console.log("Transaction successfully committed!");
} catch (e) {
  console.log("Transaction failed: ", e);
}

Upvotes: 1

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