node.js Firestore 将值添加到数组字段
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Firestore Add value to array field
提问by Kravitz
Im trying to use Firebase cloud functions to add the id of a chatroom to the users document in an array field. I cant seem to figure out the way to write to an array field type. here is my cloud function
我正在尝试使用 Firebase 云函数将聊天室的 id 添加到数组字段中的用户文档中。我似乎无法弄清楚写入数组字段类型的方法。这是我的云功能
exports.updateMessages = functions.firestore.document('messages/{messageId}/conversation/{msgkey}').onCreate( (event) => {
console.log('function started');
const messagePayload = event.data.data();
const userA = messagePayload.userA;
const userB = messagePayload.userB;
return admin.firestore().doc(`users/${userA}/chats`).add({ event.params.messageId }).then( () => {
});
});
here is the way my database looks
这是我的数据库的样子
any tips greatly appreciated, Im new to firestore.
非常感谢任何提示，我是 Firestore 的新手。
回答by Sean Blahovici
From the docs, they added a new operation to append or remove elements from arrays. Read more here: https://firebase.google.com/docs/firestore/manage-data/add-data
从文档中，他们添加了一个新操作来添加或删除数组中的元素。在此处阅读更多信息：https: //firebase.google.com/docs/firestore/manage-data/add-data
Example:
例子：
var admin = require('firebase-admin');
// ...
var washingtonRef = db.collection('cities').doc('DC');
// Atomically add a new region to the "regions" array field.
var arrUnion = washingtonRef.update({
regions: admin.firestore.FieldValue.arrayUnion('greater_virginia')
});
// Atomically remove a region from the "regions" array field.
var arrRm = washingtonRef.update({
regions: admin.firestore.FieldValue.arrayRemove('east_coast')
});
回答by Sebastian Schmidt
Firestore currently does not allow you to update the individual fields of an array. You can, however, replace the entire contents of an array as such:
Firestore 目前不允许您更新数组的各个字段。但是，您可以像这样替换数组的全部内容：
admin.firestore().doc(`users/${userA}/chats`).update('array', [...]);
Note that this might override some writes from another client. You can use transactions to lock on the document before you perform the update.
请注意，这可能会覆盖来自另一个客户端的某些写入。在执行更新之前，您可以使用事务来锁定文档。
admin.firestore().runTransaction(transaction => {
return transaction.get(docRef).then(snapshot => {
const largerArray = snapshot.get('array');
largerArray.push('newfield');
transaction.update(docRef, 'array', largerArray);
});
});
