Question

我已尝试使用Firebase云功能发送通知。我的项目结构

这是index.js，

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.pushNotification = functions.database.ref('/messages').onWrite( event => {
console.log('Push notification event triggered');

    const message = event.data.val();
    const user = event.data.val();
    console.log(message);
    console.log(user);

    const topic = "myTopic";
    const payload = {
        "data": {
            "title": "New Message from " + user,
            "detail":message,
        }
    };

    return admin.messaging().sendToTopic(topic, payload);
   });

上面的代码配置错误，当我在Node.js中部署时，LOG中的函数显示：

“TypeError：无法读取未定义的属性'val'。

实际上我正在尝试做什么：我正在尝试将快照加载中的信息提取到index.js中，以便在将新子项添加到实时数据库时，它应该触发带有标题和正文的通知负载。

在Android中，我使用子监听器，在添加新记录时进行监听

FirebaseDatabase.getInstance().getReference().child("messages")

 OnChildAdded(.....){
 if (dataSnapshot != null) {
                    MessageModel messageModel = dataSnapshot.getValue(MessageModel.class);
                    if (messageModel != null) {
                            // do whatever
                           }
                   }

但是在index.js中，我无法解析它。根据我的数据库结构如何固定index.js的一点指导将非常感激。 PS-我从未在JS中编码如果你想要更多的背景，我很乐意提供它。

Answer 1

改变这个：

exports.pushNotification = functions.database.ref('/messages').onWrite( event => {

const message = event.data.val();
const user = event.data.val();
});

到此：

exports.pushNotification = functions.database.ref('/messages').onWrite(( change,context) => {

const message = change.after.val();
});

请检查：

https://firebase.google.com/docs/functions/beta-v1-diff#realtime-database

云功能已更改，现在onWrite有两个参数change和context

change有两个属性before和after，其中每个属性都是DataSnapshot，其中列出的方法如下：

https://firebase.google.com/docs/reference/admin/node/admin.database.DataSnapshot

Answer 2

'use strict'

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);

exports.sendNotification = functions.database.ref('/NOTIFICATIONS/{UserId}/{{notification_id}').onWrite((change, context) => 
{
    const UserId = context.params.UserId;
    const notification = context.params.notification;

    console.log('The user Id is : ', UserId);

    if(!change.after.exists())
    {
        return console.log('A Notification has been deleted from the database : ', notification_id);
    }

    if (!change.after.exists()) 
    {
        return console.log('A notification has been deleted from the database:', notification);
        return null;
    }

    const deviceToken = admin.database().ref(`/USER/${UserId}/device_token`).once('value');

    return deviceToken.then(result => 
    {
        const token_id = result.val();
        const payload = {
            notification : {
                title : "Friend Request",
                body : "You've received a new Friend Request",
                icon : "default"
            }
        };

        return admin.messaging().sendToDevice(token_id, payload).then(response => {

            console.log('This was the notification Feature');
        });
    });
});

Firebase TypeError：无法读取未定义

2 个答案: