How to trigger function when date stored in firest

I am creating an app where I need to send push notification when today's date matches with the date stored in database in order to send push notification. How to achieve this?

回答1:

Without knowing your data model it is difficult to give a precise answer, but let's imagine, to simplify, that you store in each document a field named notifDate with format DDMMYYY and that those documents are store in a Collection named notificationTriggers.

You could write an HTTPS Cloud Function as follows:

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

const cors = require('cors')({ origin: true });
const moment = require('moment');

admin.initializeApp();

exports.sendDailyNotifications = functions.https.onRequest((request, response) => {

    cors(request, response, () => {

       const now = moment();
       const dateFormatted = now.format('DDMMYYYY');

       admin.firestore()
       .collection("notificationTriggers").where("notifDate", "==", dateFormatted)
       .get()
       .then(function(querySnapshot) {

           const promises = []; 

           querySnapshot.forEach(doc => {

               const tokenId = doc.data().tokenId;  //Assumption: the tokenId is in the doc
               const notificationContent = {
                 notification: {
                    title: "...",
                    body: "...",  //maybe use some data from the doc, e.g  doc.data().notificationContent
                    icon: "default",
                    sound : "default"
                 }
              };

              promises
              .push(admin.messaging().sendToDevice(tokenId, notificationContent));      

          });
          return Promise.all(promises);
       })
       .then(results => {
            response.send(data)
       })
       .catch(error => {
          console.log(error)
          response.status(500).send(error)
       });

    });

});

You would then call this Cloud Function every day with an online CRON job service like https://cron-job.org/en/.

For more examples on how to send notifications in Cloud Functions, have a look at those SO answers Sending push notification using cloud function when a new node is added in firebase realtime database?, node.js firebase deploy error or Firebase: Cloud Firestore trigger not working for FCM.

If you are not familiar with the use of Promises in Cloud Functions I would suggest you watch the 3 videos about "JavaScript Promises" from the Firebase video series: https://firebase.google.com/docs/functions/video-series/

You will note the use of Promise.all() in the above code, since you are executing several asynchronous tasks (sendToDevice() method) in parallel. This is detailed in the third video mentioned above.

回答2:

Use Google Cloud Functions Scheduled Triggers https://cloud.google.com/scheduler/docs/tut-pub-sub

Using a scheduled trigger you can specify how many times to invoke your function by specifying the frequency using the unix-cron format. Then within the function you can do date check and other needed logic