I have a function that's doing calls for firebase database and return those data. I'm trying to implement a listener to this function so when the database updates, the content in my web site also updates without refresh.
My function is as follows
export const loadBookings = async () => {
const providersSnapshot = await firebase.database().ref('products').once('value');
const providers = providersSnapshot && providersSnapshot.val();
if (!providers) {
return undefined;
}
return providers;
};
After going through some documentation i have tried changing itto something like this
const providersSnapshot = await firebase.database().ref('products').once('value');
let providers = "";
providersSnapshot.on('value', function(snapshot) {
providers = snapshot.val();
});
But the code doesn't work like that. How can i listen in real time for my firebase call?
Use on('value') instead of once('value'). once() just queries a single time (as its name suggests). on() adds a listener that will get invoked repeatedly with changes as they occur.
I suggest reading over the documentation to find an example of using on(). It shows:
var starCountRef = firebase.database().ref('posts/' + postId + '/starCount');
starCountRef.on('value', function(snapshot) {
updateStarCount(postElement, snapshot.val());
});
Related
I'm new to the "async/await" aspect of JS and I'm trying to learn how it works.
The error I'm getting is Line 10 of the following code. I have created a firestore database and am trying to listen for and get a certain document from the Collection 'rooms'. I am trying to get the data from the doc 'joiner' and use that data to update the innerHTML of other elements.
// References and Variables
const db = firebase.firestore();
const roomRef = await db.collection('rooms');
const remoteNameDOM = document.getElementById('remoteName');
const chatNameDOM = document.getElementById('title');
let remoteUser;
// Snapshot Listener
roomRef.onSnapshot(snapshot => {
snapshot.docChanges().forEach(async change => {
if (roomId != null){
if (role == "creator"){
const usersInfo = await roomRef.doc(roomId).collection('userInfo');
usersInfo.doc('joiner').get().then(async (doc) => {
remoteUser = await doc.data().joinerName;
remoteNameDOM.innerHTML = `${remoteUser} (Other)`;
chatNameDOM.innerHTML = `Chatting with ${remoteUser}`;
})
}
}
})
})
})
However, I am getting the error:
Uncaught (in promise) TypeError: Cannot read property 'joinerName' of undefined
Similarly if I change the lines 10-12 to:
remoteUser = await doc.data();
remoteNameDOM.innerHTML = `${remoteUser.joinerName} (Other)`;
chatNameDOM.innerHTML = `Chatting with ${remoteUser.joinerName}`;
I get the same error.
My current understanding is that await will wait for the line/function to finish before moving forward, and so remoteUser shouldn't be null before trying to call it. I will mention that sometimes the code works fine, and the DOM elements are updated and there are no console errors.
My questions: Am I thinking about async/await calls incorrectly? Is this not how I should be getting documents from Firestore? And most importantly, why does it seem to work only sometimes?
Edit: Here are screenshots of the Firestore database as requested by #Dharmaraj. I appreciate the advice.
You are mixing the use of async/await and then(), which is not recommended. I propose below a solution based on Promise.all() which helps understanding the different arrays that are involved in the code. You can adapt it with async/await and a for-of loop as #Dharmaraj proposed.
roomRef.onSnapshot((snapshot) => {
// snapshot.docChanges() Returns an array of the documents changes since the last snapshot.
// you may check the type of the change. I guess you maybe don’t want to treat deletions
const promises = [];
snapshot.docChanges().forEach(docChange => {
// No need to use a roomId, you get the doc via docChange.doc
// see https://firebase.google.com/docs/reference/js/firebase.firestore.DocumentChange
if (role == "creator") { // It is not clear from where you get the value of role...
const joinerRef = docChange.doc.collection('userInfo').doc('joiner');
promises.push(joinerRef.get());
}
});
Promise.all(promises)
.then(docSnapshotArray => {
// docSnapshotArray is an Array of all the docSnapshots
// corresponding to all the joiner docs corresponding to all
// the rooms that changed when the listener was triggered
docSnapshotArray.forEach(docSnapshot => {
remoteUser = docSnapshot.data().joinerName;
remoteNameDOM.innerHTML = `${remoteUser} (Other)`;
chatNameDOM.innerHTML = `Chatting with ${remoteUser}`;
})
});
});
However, what is not clear to me is how you differentiate the different elements of the "first" snapshot (i.e. roomRef.onSnapshot((snapshot) => {...}))). If several rooms change, the snapshot.docChanges() Array will contain several changes and, at the end, you will overwrite the remoteNameDOM and chatNameDOM elements in the last loop.
Or you know upfront that this "first" snapshot will ALWAYS contain a single doc (because of the architecture of your app) and then you could simplify the code by just treating the first and unique element as follows:
roomRef.onSnapshot((snapshot) => {
const roomDoc = snapshot.docChanges()[0];
// ...
});
There are few mistakes in this:
db.collection() does not return a promise and hence await is not necessary there
forEach ignores promises so you can't actually use await inside of forEach. for-of is preferred in that case.
Please try the following code:
const db = firebase.firestore();
const roomRef = db.collection('rooms');
const remoteNameDOM = document.getElementById('remoteName');
const chatNameDOM = document.getElementById('title');
let remoteUser;
// Snapshot Listener
roomRef.onSnapshot(async (snapshot) => {
for (const change of snapshot.docChanges()) {
if (roomId != null){
if (role == "creator"){
const usersInfo = roomRef.doc(roomId).collection('userInfo').doc("joiner");
usersInfo.doc('joiner').get().then(async (doc) => {
remoteUser = doc.data().joinerName;
remoteNameDOM.innerHTML = `${remoteUser} (Other)`;
chatNameDOM.innerHTML = `Chatting with ${remoteUser}`;
})
}
}
}
})
exports.editData = functions.database.ref('/AllData/hello/A').onWrite((change, context) => {
const after = change.after;
if (after.exists()) {
const data = after.val();
var value = data;
// set of data to multiply by turns ratio
var actualEIn = (value.ein)*200;
console.log('Data Edited');
}
return admin.database().ref('/editedData/hello/A').push({
ein: actualEIn,
});
});
Edit: made some edits to the code as suggested! However, when I deploy it there are literally no logs.
Change this:
exports.editValues = functions.database.ref('/AllData/hello/A').onWrite((snapshot) => {
const data = snapshot.val();
if (data.exists()) {
into this:
exports.editValues = functions.database.ref('/AllData/hello/A').onWrite((change,context) => {
const data = change.after.val();
if (data.exists()) {
more info here:
https://firebase.google.com/docs/functions/beta-v1-diff#realtime-database
exports.editData = functions.database.ref('/AllData/hello/A/{id}').onWrite((change, context) => {
const afterData = change.after;
if (afterData.exists()) {
console.log('hey');
const data = afterData.val();
// set of data to multiply by turns ratio
var actualEIn = (data.ein)*200;
}
return admin.database().ref('/editedData/hello/A').push({
ein: actualEIn,
});
});
Hi guys thank you for all your help! :) I managed to solve this by adding a /{id} at the back!
You've got two things wrong here.
First, newer versions of the firebase-functions SDK since version 1.0 deliver a Change object to onWrite handlers instead of a snapshot, as it appears you are expecting. The Change object has properties for before and after with DataSnapshot objects of the contents of the database before and after the change that triggered the function. Please read the documentation for database triggers to get all the information.
Second, exists() is a method on DataSnapshot, but you're using it on the raw JavaScript object value of the contents of the database the location of change. JavaScript objects coming from val() will not have any methods to call.
You should probably update your code to:
Use the latest version of the firebase-functions module
Alter your function to accept the Change object instead of a snapshot
Use the exists() method on a snapshot in the change, rather than a raw JavaScript object.
Starter code:
exports.editValues = functions.database.ref('/AllData/hello/A').onWrite((change) => {
const after = change.after; // the DataSnapshot of the data after it was changed
if (after.exists()) {
const data = after.val() // the raw JavaScript value of the location
// use data here
}
})
I am using firebase functions and have successfully run a sanitize function.
The problem I am having is my firebase database looks like this.
The ABC123 and the 0l692lPD6EfqUZ4Y4xiCOVmnNmC2 are both sets automatically when a post is created so I would not know what they will be.
I can hard code the first ABC123 and set {postID} for the second one and it runs successfully. But if I set both to posteId it fails.
below is my code. I need to be able to change the ABC123 to postId because I will not know what it will be in my index.js code.
exports.sanitizePost = functions.database
.ref('/posts/ABC123/question/{postId}')
.onWrite(event => {
const post = event.data.val()
if (post.sanitized) {
return
}
console.log("Sanitizing new post " + event.params.pushId)
console.log(post)
post.sanitized = true
post.question = sanitize(post.question)
const promise = event.data.ref.set(post)
return promise
})
function sanitize(s) {
var sanitizedText = s
sanitizedText = sanitizedText.replace(/\bstupid\b/ig, "wonderful")
return sanitizedText
}
I need .ref('/posts/ABC123/question/{postId}') to be .ref('/posts/{postID}/question/{postId}') or somthing that works.
You cannot have the same parameter twice in a path. But you can have two parameters of different names, e.g.
exports.sanitizePost = functions.database
.ref('/posts/{questionId}/question/{postId}')
I am trying to create a function for my database using Cloud Functions for Firebase. The purpose of the function is to listen to write events on the attend table and based on the object written to identify the event and increment the usersAttending on the event object.
This is my function so far.
//listens to write on attendObjects (when a user is attending an event), and increments attending users for event
exports.listenAttendingEvents = functions.database.ref('/attend/{pushId}').onWrite(event => {
//get attendObj -> parsed JSON by javascript interpreter
const attentObj = event.data.val();
const attendId = attentObj['attendId'];
const pathToAttendees = '/attends' + '/' + attendId;
// Attach an asynchronous callback to read the data at our posts reference
admin.database().ref(pathToAttendees).on("value", function(snapshot) {
console.log(snapshot.val());
const obj = snapshot.val();
var nrAttending = obj['attending'];
nrAttending = Number(snapshot.val());
return admin.database().ref(pathToAttendees + '/attending').transaction(function (nrAttending) {
return (nrAttending || 0) + 1;
});
});
}, function (errorObject) {
console.log("The read failed: " + errorObject.code);
return errorObject
});
The problems as it seems is that the event object doesn't get retrieved. The function seems to finish before that with the status ok
The problem was that I was not having a promise for my top-level function. This caused Google Cloud Functions to kill it before the operation was complete.
Adding a promise solved my problem
admin.database().ref(pathToAttendees).once("value").then( function(snapshot) {
I'm using this Gumroad-API npm package in order to fetch data from an external service (Gumroad). Unfortunately, it seems to use a .then() construct which can get a little unwieldy as you will find out below:
This is my meteor method:
Meteor.methods({
fetchGumroadData: () => {
const Gumroad = Meteor.npmRequire('gumroad-api');
let gumroad = new Gumroad({ token: Meteor.settings.gumroadAccessKey });
let before = "2099-12-04";
let after = "2014-12-04";
let page = 1;
let sales = [];
// Recursively defined to continue fetching the next page if it exists
let doThisAfterResponse = (response) => {
sales.push(response.sales);
if (response.next_page_url) {
page = page + 1;
gumroad.listSales(after, before, page).then(doThisAfterResponse);
} else {
let finalArray = R.unnest(sales);
console.log('result array length: ' + finalArray.length);
Meteor.call('insertSales', finalArray);
console.log('FINISHED');
}
}
gumroad.listSales(after, before, page).then(doThisAfterResponse); // run
}
});
Since the NPM package exposes the Gumorad API using something like this:
gumroad.listSales(after, before, page).then(callback)
I decided to do it recursively in order to grab all pages of data.
Let me try to re-cap what is happening here:
The journey starts on the last line of the code shown above.
The initial page is fetched, and doThisAfterResponse() is run for the first time.
We first dump the returned data into our sales array, and then we check if the response has given us a link to the next page (as an indication as to whether or not we're on the final page).
If so, we increment our page count and we make the API call again with the same function to handle the response again.
If not, this means we're at our final page. Now it's time to format the data using R.unnest and finally insert the finalArray of data into our database.
But a funny thing happens here. The entire execution halts at the Meteor.call() and I don't even get an error output to the server logs.
I even tried switching out the Meteor.call() for a simple: Sales.insert({text: 'testing'}) but the exact same behaviour is observed.
What I really need to do is to fetch the information and then store it into the database on the server. How can I make that happen?
EDIT: Please also see this other (much more simplified) SO question I made:
Calling a Meteor Method inside a Promise Callback [Halting w/o Error]
I ended up ditching the NPM package and writing my own API call. I could never figure out how to make my call inside the .then(). Here's the code:
fetchGumroadData: () => {
let sales = [];
const fetchData = (page = 1) => {
let options = {
data: {
access_token: Meteor.settings.gumroadAccessKey,
before: '2099-12-04',
after: '2014-12-04',
page: page,
}
};
HTTP.call('GET', 'https://api.gumroad.com/v2/sales', options, (err,res) => {
if (err) { // API call failed
console.log(err);
throw err;
} else { // API call successful
sales.push(...res.data.sales);
res.data.next_page_url ? fetchData(page + 1) : Meteor.call('addSalesFromAPI', sales);
}
});
};
fetchData(); // run the function to fetch data recursively
}