如何在用户之间发送推送通知？

Question

Trying to send push notification from user-to-user, UserA is bidding on the value for an item. Scenario, UserA updates a value in the app and clicks send, and at the same time UserB gets a notification of the updated value.

       If UserB approves of the message(value) {
           UserA gets gets the notification of approval and proceeds to 
      final step of buying the item. 
 }  else {
sends no and UserA is updated of the denial and he sends a new value for approval
}

A guide to accomplish the task would be greatly appreciated.

PS using firebase as backend

Answer 1

Since you are already using Firebase, you have it pretty easy.

This tutorial explains everything you need to do this:

https://www.raywenderlich.com/140836/firebase-tutorial-real-time-chat-2

Essentially you need to do two things:

1. Save data to the Firebase database. (User A)
2. Listen for new data being saved to the database. (User B)

Additionally, the firebase docs themselves explain this pretty well: https://firebase.google.com/docs/cloud-messaging/ios/topic-messaging

Answer 2

You can use Firebase with the cloud messaging. So UserA creates the item. UserB is interested so he would subscribe to a topic about that item.

And every time there is an update, he would get a notification. Check this https://firebase.google.com/docs/cloud-messaging/ios/topic-messaging

Answer 3

Sending Push Notifications is done with Apple Push Notification Service. Apple provides a documentation on how to use APNs.

The basic principal is illustrated in this picture.

Sending Messages from one device directly to another is not the way it works. You have to send a notification to the APNs in order to push them to another devices.

Since you are using Firebase I would recommend using Firebase Cloud Messaging to send Push Notifications.

If you just need real time updates in the app Firebase event listeners should work just fine.