how to send silent notification / background notification using Firebase Cloud Messaging? - ios

Question

I need to make silent notification/background notification in my iOS app using Firebase Cloud Messaging, so I can make an update in the app even though the user doesn't tap the push notification.
the documentation from Apple about background notification is in here , it is said that
To send a background notification, create a remote notification with
an aps dictionary that includes only the content-available key in the payload
Sample payload for a background notification from that documentation is like this:
{
"aps" : {
"content-available" : 1
},
"acme1" : "bar",
"acme2" : 42
}
so I create my own payload when sending FCM using cloud function node JS. my code is like this
const userToken = device.token
const payload = {
data: {
notificationID : notificationID,
creatorID : moderatorID,
creatorName: creatorName,
title : title,
body : body,
createdAt : now,
imagePath : imagePath,
type: type
},
apps : {
"content-available" : 1 // to force background data update in iOS
}
}
await admin.messaging().sendToDevice(userToken,payload)
I try to send and I have error:
'Messaging payload contains an invalid "apps" property. Valid
properties are "data" and "notification".
so adding "apps" property is not allowed, but iOS documentation said that I need to add "content-available" in the payload.
I read other answer in here, it is said that the payload should be written like this
{
"to" : "[token]",
"content_available": true,
"priority": "high",
"data" : {
"key1" : "abc",
"key2" : abc
}
but I am confused how to write the payload FCM that can trigger background notification in iOS

Answer 1

Based on the error message that you are receiving, you should remove the apps property since data and notification properties are considered to be valid, as per the documentation.
Now, in regards to the the payload that you found elsewhere, this refers to the HTTP syntax used to pass messages from your app server to client apps via Firebase Cloud Messaging using the FCM legacy HTTP API. You can refer to the the documentation to learn more about the new HTTP v1 API.
To answer your question, when you are using a Cloud Function with Node.js runtime to send notifications using the sendToDevice(token, payload, options) method, you will need to pass the contentAvailable in the function's options parameter.
The contentAvailable option does the following: When a notification or message is sent and this is set to true, an inactive client app is awoken, and the message is sent through APNs as a silent notification and not through the FCM connection server.
Therefore, your Cloud Function might look something like this:
const userToken = [YOUR_TOKEN];
const payload = {
"data": {
"story_id": "story_12345"
},
"notification": {
"title": "Breaking News"
}
};
const options = {
"contentAvailable": true
};
admin.messaging().sendToDevice(userToken, payload, options).then(function(response) {
console.log('Successfully sent message:', response);
}).catch(function(error) {
console.log('Error sending message:', error);
});