Firebase-当存储到某些用户的新数据在数据库中有特定数据时，发送通知

Question

当实时数据库有新数据时，我想向在Firebase Firestore中有特定数据的用户发送通知。

与用户有关系的数据示例。

Firebase实时数据后

并且用户拥有他所关注的群组。

Firebase Firestore-用户数据

截至目前，具体数据为组名。

轻松地，向与海报组名具有相同组名的用户发送通知

Answer 1

与其在Cloud Firestore中搜索用户以进行通知，不如使用Firebase Cloud Messaging。这允许您为每个用户订阅与他们所在的组相对应的主题。

因为你需要为每个相关用户订阅他们相应的通知主题，所以这不是一个简单的"；顺便拜访一下就行了"；解决方案有关如何做到这一点，请参阅目标平台的文档。

import * as functions from "firebase-functions";
import * as admin from "firebase-admin";
export const notifyGroupsOfNewPost = functions.database.ref("/Poster/{postId}").onCreate(async (snapshot, context) => {
/* avoid using `snapshot.val()` unless you need all of the data at once */

const postGroups = snapshot.child("Groups").val(); // assumed to be parsed as an array, make sure to handle non-array values gracefully

if (postGroups === null) {
throw new Error('Groups of new post missing');
}

return Promise.all(postGroups.map((group) => {
const message = {
/* note: only send data used for creating the notification message,
the rest of it can be downloaded using the SDK once it's needed */
data: { 
Impact: snapshot.child("Impact").val(),
Subject: snapshot.child("Subject").val(),
TT: snapshot.child("TT").val()
},
topic: group /* you could also use `${group}-newpost` here */
};

return admin.messaging().send(message)
.then((messageId) => {
console.log(`Successfully notified the ${group} group about new post #${snapshot.key} (FCM #{$messageId})`);
})
.catch((error) => {
console.error(`Failed to notify the ${group} group about new post #${snapshot.key}:`, error);
});
});
});