How to schedule push notifcations for react native expo?

Question

I am trying to send push notifications to a user at a scheduled time. Say they set the date for an event and they want to be notified 30 minutes before, that is when I would like to send them a notification. I am using firebase as my backend and the project is built with expo.

I am curious how I would use expo's notification system if I am using firebase cloud messaging because it says I need separate permission from firebase (I already have the expo token for each user). I have looked into node cron/schedule and also react-native push notification but I am unsure which would be the best solution and where I would deploy the solution (such as running a cloud function).

I assume I need some type of function that takes the token, message body, title, and date and then sets it up to schedule it either to the server or locally. And then that function would be called when they press the button to receive the notification. They can also change the date of the event so it would need to switch the date if the user did that.

Any advice would be greatly appreciated as I have been researching this for days and still am unsure of the best approach.

Answer 1

One possible approach:

1. In your backend, schedule a cron job that runs every minute (or every 15 seconds) and checks against database which events have start time within next 30 mins.

2. Once you have the events , find out the users registered for those events and collect their user ids.

3. As you mention that you already have stored the tokens, so I assume that those tokens exist in some table against the user id. (eg mapping of user-id and tokens ). Look up this table to fetch the tokens of those users.

4. Prepare the notification payload and call firebase messaging to send notification against the token. For example, at this point you can call the sendToDevice() function from Firebase SDK: firebase.messaging().sendToDevice(tokens, payload);

Now you can implement these steps in your backend (eg Nodejs) or you can deploy a cloud function for this and setup scheduling for this cloud function.

Let me know if you need any further help!