使用Cloud Functions for Firebase发送推送通知

Question

我试图制作一个云函数，向给定用户发送消息推送。

用户进行一些更改，并在firebase数据库中的节点下添加/更新数据（该节点表示用户id）。这里我想触发一个函数，它向用户发送推送通知。

对于DB中的用户，我有以下结构。

Users

 - UID
 - - email
 - - token

 - UID
 - - email
 - - token

到目前为止，我有这个功能：

exports.sendNewTripNotification = functions.database.ref('/{uid}/shared_trips/').onWrite(event=>{
const uuid = event.params.uid;

console.log('User to send notification', uuid);

var ref = admin.database().ref('Users/{uuid}');
ref.on("value", function(snapshot){
        console.log("Val = " + snapshot.val());
        },
    function (errorObject) {
        console.log("The read failed: " + errorObject.code);
});

当我得到回调时，snapshot.val（）返回null。知道怎么解决这个问题吗？也许之后如何发送消息推送？

Answer 1

返回此函数调用。

return ref.on("value", function(snapshot){
        console.log("Val = " + snapshot.val());
        },
    function (errorObject) {
        console.log("The read failed: " + errorObject.code);
});

这将使云功能保持活动状态，直到请求完成。从Doug在评论中给出的链接了解更多关于返还promise的信息。

Answer 2

只是回答Jerin A Mathews的问题。。。使用以下主题发送消息：

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

admin.initializeApp(functions.config().firebase);

//Now we're going to create a function that listens to when a 'Notifications' node changes and send a notificcation
//to all devices subscribed to a topic

exports.sendNotification = functions.database.ref("Notifications/{uid}")
.onWrite(event => {
    //This will be the notification model that we push to firebase
    var request = event.data.val();

    var payload = {
        data:{
          username: request.username,
          imageUrl: request.imageUrl,
          email: request.email,
          uid: request.uid,
          text: request.text
        }
    };

    //The topic variable can be anything from a username, to a uid
    //I find this approach much better than using the refresh token
    //as you can subscribe to someone's phone number, username, or some other unique identifier
    //to communicate between

    //Now let's move onto the code, but before that, let's push this to firebase

    admin.messaging().sendToTopic(request.topic, payload)
    .then((response) => {
        console.log("Successfully sent message: ", response);
        return true;
    })
    .catch((error) => {
        console.log("Error sending message: ", error);
        return false;
    })
})
//And this is it for building notifications to multiple devices from or to one.

Answer 3

我设法使这项工作。下面是使用云函数发送通知的代码，对我有效。

exports.sendNewTripNotification = functions.database.ref('/{uid}/shared_trips/').onWrite(event=>{
    const uuid = event.params.uid;

    console.log('User to send notification', uuid);

    var ref = admin.database().ref(`Users/${uuid}/token`);
    return ref.once("value", function(snapshot){
         const payload = {
              notification: {
                  title: 'You have been invited to a trip.',
                  body: 'Tap here to check it out!'
              }
         };

         admin.messaging().sendToDevice(snapshot.val(), payload)

    }, function (errorObject) {
        console.log("The read failed: " + errorObject.code);
    });
})