Firestore add() in forEach 循环不起作用

Question

我正试图创建一个Firebase函数，将子集合从一个用户克隆到另一个用户。

但是，我在最后一步遇到了问题：向新用户添加子集合文档。

这是我的功能：

import { Firestore } from '@google-cloud/firestore';
exports.handler = async function(req: any, res: any, db: Firestore) {
const fromUid = req.body.from;
const toUid = req.body.to;
let transactionCount = 0;
const userToRef = await db
.collection('users')
.doc(toUid)
.collection('transactions');
await userToRef.add({ ...{ data: 'some-dummy-data' } }); // At this point I get write to the collection
const transactions = await db
.collection(`users/${fromUid}/transactions`)
.get();
const transactionsList: any[] = [];
transactions.forEach((doc: any) => {
const transaction = doc.data();
transaction.uid = toUid;
transactionsList.push(transaction);
userToRef.add({
// Here write to the collection doesnt work
...transaction
});
transactionCount++;
});
console.log(transactionsList);
res.send(
`Successfully cloned ${transactionCount} transactions from ${fromUid} to ${toUid}.`
);
return '';
};

在上面的代码示例中，我对用户子集合进行了两次写入(请参阅代码注释(。第一个工作正常，第二个不正常。

知道为什么我不能在forEach循环中写吗？

Answer 1

您应该使用Promise.all()，以便在通过res对象将响应发送回客户端之前，等待对userToRef集合的所有写入完成。

以下经过调整的代码应该可以工作(未经测试(。

然而，我不清楚你最后应该做什么，因为我们不知道你是如何调用这个函数的(你可能是从云函数本身调用它的？(。您可能不需要执行return '';，因为执行res.send((实际上是在终止函数。为了供您参考，我在下面添加了一个经过测试的HTTPS云函数的完整代码，该函数执行类似的集合写入。

exports.handler = async function (req: any, res: any, db: Firestore) {
const fromUid = req.body.from;
const toUid = req.body.to;
let transactionCount = 0;
const userToRef = await db
.collection('users')
.doc(toUid)
.collection('transactions');
await userToRef.add({ ...{ data: 'some-dummy-data' } }); // At this point I get write to the collection
const transactions = await db
.collection(`users/${fromUid}/transactions`)
.get();
//const transactionsList: any[] = [];
const promises: Promise<DocumentReference>[] = [];
transactions.forEach((doc: any) => {
const transaction = doc.data();
transaction.uid = toUid;
//transactionsList.push(transaction);
promises.push(
userToRef.add({
// Here write to the collection doesnt work
...transaction
}));
transactionCount++;
});
//console.log(transactionsList);
await Promise.all(promises);
res.send(
`Successfully cloned ${transactionCount} transactions from ${fromUid} to ${toUid}.`
);
//return '';
};

---

以下是HTTPS云函数的代码，它实现了一组类似的集合写入：

import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';
import { DocumentReference } from '@google-cloud/firestore';
admin.initializeApp();
export const helloWorld = functions.https.onRequest(async (req, res) => {
const db = admin.firestore();
let writeCount = 0;
const theArray: string[] = ['AA', 'BB', 'CC'];
const promises: Promise<DocumentReference>[] = [];
theArray.forEach((value: string) => {
promises.push(db.collection('testCollection').add({ val: value }));
writeCount++;
});
await Promise.all(promises);
res.send(`Successfully wrote ${writeCount} documents.`);
});