javascript - How to add child to a List in Firebase Realtime Database with a cloud function?

Question

I try to create a Firebase cloud function that react on new "Event" in the realtime database and add a "notification" object in a notification list for the corresponding users. i succeed to get new event information,to push a notification a corresponding users but not in a list format (but in hashmap format).

So I tried to get the numbers of children in order to push new notification with the good index. I don't know how to manage promises in that case.

The idea is to get sport_name and level from the new event, to get corresponding users in Sport and add notification for each users.

There is my cloud function :

exports.detectEvent = functions.database
.ref("Event/{eventID}")
.onCreate((snapshot, context) => {
    const event = snapshot.val();
    const sport = event.sport.name;
    const level = event.niveau;
    const name = event.name;
    var promises=[];
    var path = "Sports/" + sport + "/" + level;
    var notif = {
        type : "Event",
        contentID : context.params.eventID,
        message : sport + " : Un nouvel événement vous correspond ! ",
        seen : false,
        date : "01"
    };
    console.log('path ', path);
    return admin.database().ref(path).once("value", function(result) {
        var datas = result.val();
        for (var property in datas)  {
            if (datas.hasOwnProperty(property)) {
                promises.push(admin.database().ref("Users/"+datas[property]+"/notifications").on("value", function(snapshot) {
                    console.log("There are "+snapshot.numChildren()+" notifs");
                    admin.database().ref("Users/"+datas[property]+"/notifications").child(snapshot.numChildren()).set(notif)
                  }));

        }

    }
    return Promise.all(promises);
})

});

There is the table :

Table

You have two return statements in your function. That can't possibly be what you want - a function can only return one value. Also, you are not dealing with promises correctly. Lastly, you should almost never use on(). Use once() instead to get data a single time. — Doug Stevenson
Thank you for your answer. Do you have an idea of how to do it? — Naadril

Naadril Naadril · Accepted Answer · 2018-12-05T19:05:26

This code works but it create a random key for notifications. How to put integer (0,1,2,...) as key in order to have a list in my database ?

<pre>
exports.detectEvent = functions.database
.ref("Event/{eventID}")
.onCreate((snapshot, context) => {
    const event = snapshot.val();
    const sport = event.sport.name;
    const level = event.niveau;
    const name = event.name;
    var promises=[];
    var path = "Sports/" + sport + "/" + level;
    var notif = {
        type : "Event",
        contentID : context.params.eventID,
        message : sport + " : Un nouvel événement vous correspond ! ",
        seen : false,
        date : "01"
    };
    console.log('path ', path);
    return admin.database().ref(path).once("value", function(result) {
        var datas = result.val();
        for (var property in datas)  {
            if (datas.hasOwnProperty(property)) {
                promises.push(admin.database().ref("Users/"+datas[property]+"/notifications").push(notif));
            }

        }
        return Promise.all(promises);
    })
});

<code>

javascript - How to add child to a List in Firebase Realtime Database with a cloud function?

1 Answers