I have a webserver that sent a client a push notification. The client can intercept the push notification with UNNotificationServiceExtension on iOS 10 and change the content. Now I want to cancel a push notification from showing on client side on certain notifications. How do I do that? I tried to do
self.contentHandler(nil);
but it didn't work. How to do it?
It look like it might not be possible, but not sure. From the docs:
You can modify any of the content from the original request. You might
customize the content for the current user or replace it altogether.
You can use this method to download images or movies and add them as
attachments to the content. You may also modify the alert text as long
as you do not remove it. If the content object does not contain any
alert text, the system ignores your modifications and delivers the
original notification content.
https://developer.apple.com/reference/usernotifications/unnotificationserviceextension/1648229-didreceivenotificationrequest?language=objc
Calling the block with nil just displays the original notification?
It's now possible since iOS 13.3. You need to pass an empty UNNotificationContent to contentHandler (not nil) and add the new filtering entitlement.
// Determine whether you should suppress the notification.
let suppress = myShouldSuppressNotification(request: request)
if suppress {
// Don't deliver the notification to the user.
contentHandler(UNNotificationContent())
} else { ///...
Reference : https://developer.apple.com/documentation/bundleresources/entitlements/com_apple_developer_usernotifications_filtering
I think the easiest way would be to send every push notification as a silent notification by default and only show the ones that you want to show. When you get a silent notification in
func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any])
You check your notification and determine if it should be displayed to the user. If not, you do nothing with it. If it needs to be shown then create a local notification and display it UILocalNotification (iOS 9 and earlier) or UNNotification (iOS 10).
I should add this has the disadvantage that no notifications will show if the app is not resident in memory (because the app needs to make the silent notification into a local notification), but if you were to take the opposite tact then you have the problem that something might be shown that shouldn't be show.
On iOS 10 and above you can send you a "silent" notification:
Apple doc: configure silent notification
Then you can decide if the notification should be shown to the user, if so, just create a user notification and show it:
Apple doc: local and push notifications
#Jorge Arimany's answer is to send the silent notification to wake up devices to do something, I think it's not the solution this user wants. And I think we still will get the general notification if we do nothing in our UNNotificationServiceExtension class
Pre iOS 10: I dont think it is possible. Here are the reasons. Once when the server sends a push notification to the client to Apple APNS server to send it to the clients, you lose the control of the push notifications. This is one of the reasons apple doesn't always promise 100 percent delivery of the notifications. This implicitly tells you that the Push notifications on the iPhone is handled by the iPhone operating system rather than your App.
Even the push notifications displayed in the Apple iPhone Springboard/dashboard is not in your control.
Users can either control whether he wants to receive the notifications or not.
So i don't think you can control the notifications partly after it is sent from your server.
Related
I have a weird feature I'm looking to add to iOS and am not sure if it's possible.
I want to send push notifications to all users through a third party and have the client decide whether or not to show it depending on some feature. I was reading that I can modify the notification before it reaches the app and was hoping that I could receive the notification, do some logic and, if the criteria is satisfied, modify the notification to be silent. But I'm not sure if this is possible.
Has anybody been able to do this?
As far as I know, it's not possible to hide a notification after it was sent.
You can modify the payload through a service extension but I'm pretty sure you cannot hide it from the user.
To decide on the client if a notification is visible or not - you'll have to send your notification as silent to begin with and then trigger a local notification.
The problems with that are:
Silent notifications are disabled if the user disabled Background Activity.
Silent notifications have a lower priority and might be throttled after a while.
The purpose of silent pushes is to inform the app of new content to perform a background fetch.
My recommendation is to put whatever logic you want on the server side before sending the notification.
For Android you can decide whether to show the notification or not.
For iOS, you can only modify the way the notification is presented but you cannot stop it from being shown. In order to modify the way the notification is presented to the user on iOS you need to add a Notification Extension Service.
When I read Apple Docs, they mention 3 types of notification: local, remote, and silent.
Local notification can be inferred from its name, that is sent by the app locally.
However, what is the difference between the other two types?
EDIT: While this answer is fully applicable, there are some additions (not changes) to notifications in iOS 12. I highly recommend watching WWDC 2018: What’s New in User Notifications and read this amazing and must read article.
Main changes are:
grouped notifications along with summary format
provisional notifications ie show notifications directly in notification center without user permission
critical notifications which ignore 'do not disturb' or 'mute'
ability to interact with the notifications in the extensions
ability to completely reset or update actions
ability to deeplink into app's notification Settings from phone's Notification Center
IMPORTANT NOTE: Not sure since when but from the Apple docs, the 'silent notification' has been renamed to 'background notification'
There are too many settings that need to be set right for it to work. I'll try to dissect them and make them easier to understand.
Overall, several things are important.
the overall difference between a silent and user notification
different types of user notifications
how a remote notification, i.e. the payload, is configured from your server
how to enable push notifications and remote notifications from background modes on your project
how to register your token with APNs for remote and silent notifications and APNs architecture
how to request permission for user notifications
enabling 'background app refresh' and 'notifications' from the device
what is content-available
understanding that the iOS is upstream to your app when it comes to receiving a remote notification
what happens when the OS receives notifications when the app has been user-terminated
A note on reliability and APNs architecture
I highly recommend everyone to watch the first 7 minutes of: WWDC 2015: What's new in Notifications. From there, the presenter mentions that there are 2 major types of notifications:
Silent Notifications
They happen in the background, hence you never see any alert/badge/sound. Things get downloaded without you knowing about them.
iOS 11 bug
See here.
iOS 11 initial releases were buggy for silent notifications. Make sure
you have the latest version for your testing, otherwise, it may not
work
User Notifications
As the name says, it has something to do with the user. That is, the user will see an alert/badge or hear a sound. It has 2 types.
Local Notifications
A Local Notification can be triggered in 3 different ways:
UNLocationNotificationTrigger:
You see an alert when you're close to a Walmart store.
UNTimeIntervalNotificationTrigger: e.g. You see an alert every 10 minutes.
UNCalendarNotificationTrigger like December 1st 1:00PM 2017.
Remote Notifications
They are similar to local notifications but they are triggered from the server, e.g. a WhatsApp message that has a From field (Mom) and a body field (I love you!).
Token registration and APNs architecture:
To receive a silent or remote notification, you need to register for a token using:
application.registerForRemoteNotifications()
👆 Registering does NOT require user permission. This makes silent notifications to become seamless. See this moment of the WWDC video
Silent notifications are enabled by default. The user does not need
to approve your -- does not give permission to your app to use them,
and you can just start using them without asking the user for
permission.
From WWDC
Remember APNs is delivered to your users by APNs and not by your server. So your iOS code must send this token to your server. So the server can associate a given device token with the user. When you want to push to a certain user, your server just tells APNs to send a payload to a specific token. What's important to understand is that your server and APNs are two different things
The flow of it looks like this:
Â
Â
server/provider sends a payload to APNs
APNs send a notification to all target devices of a given account. e.g. your iPhone, Mac could both receive notifications for emails/messages.
Then your iPhone/Mac will deliver that message to the app. APNs don't directly send messages to your app. It sends it to the device. Then the iOS sends it to your app.
For more on this see docs APNs Overview and Sending Notification Requests to APNs
To be able to show badges/alerts/sounds, you need to request permission from the user:
UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound]) { (granted, error) in
guard error == nil else {
//Display Error.. Handle Error.. etc..
return
}
if granted {
//Do stuff here..
//Register for RemoteNotifications. Your Remote Notifications can display alerts now :)
application.registerForRemoteNotifications()
}
else {
//Handle user denying permissions..
}
}
Question: Do I need to request access once for local notifications and once for remote notifications?
No. Just write the snippet above and it will request access for both remote and local.
Now let's get to the tricky part :D
Xcode Project + iPhone Settings
Do I need to enable something to receive silent notifications?
You must enable Push Notifications from your Xcode capabilities:
If you don't enable this, your app won't receive a token. And without a token, the server doesn't recognize you.
To be able to download stuff from the background, you need to enable: remote notifications from background modes.
To enable backgroundModes, you can do it either using your plist or Xcode capabilities.
The reason you can do it, either way, is because plist is closer to your code and is the old way, perhaps it's there for legacy support. Xcode capabilities is the newer, easy way.
plist:
Item 0 is just an index, it's not the key of a dictionary (something you normally see in plist), the UIBackgroundModes is an array of Strings. The strings must only come from an accepted value from the UIBackgroundModes Array.
Xcode Capabilities:
Check the Remote Notification in Xcode under background modes as below:
If you don't do any of the above, then toggling off notifications with:
will kill Remote & Local Notifications
However, if you do enable background app refresh from plist or Xcode capabilities, then even with notifications turned off for the app, you will still receive silent notifications!
If the user wants to disable silent notifications, he would have to disable both notifications and disable 'background app refresh for your app / across the system.
To disable 'background app refresh' across your system, you have to do this:
Why am I saying all this? To explain to you that settings of silent and push notifications are different for the user and the restrictions for sending them are different. For more, see this moment from the WWDC video. See here instead (the previous link was dead):
Silent notifications are enabled by default.
The user does not need to approve your does not give permission to
your app to use them, and you can just start using them without asking
the user for permission.
But silent notifications are the mechanism behind background app
refresh.
At any point you know that the user can go in settings and disable
them.
So you can't depend on them always being available.
You don't know if the user the turn them off, and you are not getting
a notification anymore.
This also means that silent notifications are delivered with the best
effort.
That means that when the notification arrives on the user's device,
the system is going to make some choices.
It's going to use different signals from the device and from the user
behavior, like power or the time of day to decide when it is a good
time to deliver the notification and launch your app.
It may try to save battery or it may try to match the user behavior
and make the content available when the user is more likely to use it.
Also see here.
CAVEAT: Even if you disable app background refresh and disable allow notifications, you can still receive silent notifications if your app is in FOREGROUND. If your app is in the background, it won't be delivered.
Do I need to enable something to receive remote notifications?
You just need to enable Push Notifications from your Xcode capabilities:
If you don't enable this, your app won't receive a token. And without a token, the server doesn't recognize you.
APNs Payload structure
Curious... Can you tell me what should my payload look like?
I highly recommend you see Apple§ documentation. It's very clear AND ALSO SEE Sending Notification Requests to APNs. Basically platform makes an HTTP/2 call to APNs and sends the desired payload. Sending the correct headers is critical otherwise your notifications are not delivered to the devices!
Thanks, but can you just tell me the important parts?
uhhmm... OK, but just so you know this is from the link I just said:
For Silent Notifications there is a single criterion:
The payload's aps dictionary must include the content-available key
with a value of 1.
Per docs you can send other fields
If there are user-visible updates that go along with the background
update, you can set the alert, sound, or badge keys in the aps
dictionary, as appropriate.
A sample payload would look like this:
{
"aps" : {
"content-available" : 1
},
"acme1" : "bar",
"acme2" : 42
}
acme1, acme2, or just some custom data! But for the aps key, you MUST follow Apple's structure, otherwise, it won't map correctly and you won't be able to read data correctly.
Note: I haven't verified this, but another engineer mentioned that if you have provisional notifications enabled then to ensure silent notifications are delivered you must include an alert field with an empty body. For example:
{
"aps" : {
"content-available" : 1,
"alert" : {
"body" : "",
},
},
}
For User Notifications:
You need an alert key inside your aps.
As an example:
{
"aps" : {
"alert" : "You got your emails.",
"badge" : 9,
"sound" : "bingbong.aiff"
},
"acme1" : "bar",
"acme2" : 42
}
There is also a third option which I will discuss further down the answer.
As for what the fixed aps and alert dictionary keys are, see these Apple docs.
OK, got it. What is content-available?
Very simple. It's just a flag that tells your app that you need to wake up and download something because I have content available for download! For more info, see this exact moment.
By default the content-available flag is not included, i.e., by default the notifications you send won't trigger application(_:didReceiveRemoteNotification:fetchCompletionHandler:) or do something in your app. It would just show the notification. If you want to wake up the app (to do something in the background), you need to include content-available and set it to 1.
§: If you're using Firebase, your payload structure and keys may be slightly different. For example, the key content-available is replaced by content_available. For more, see Firebase documentation and also here.
I know you told me that I can only download something into my app when I'm using silent notifications, but is there a way that I can also wake my app up in the background AND download something for remote notifications?
Yes, but then similar to the silent notification, you must also set the content-available flag to 1, so it would know to wake up and download something. Otherwise, it would just pop and alert/badge/sound but won't download anything.
IMPORTANT NOTES:
If your app has only silent notifications, just enable "push notifications" + "remote notifications" from capabilities and set content-available to 1 for each payload.
If your app has only remote notifications, just enable "push notifications" from capabilities. There's nothing to do for the content-available.
However, if you want your notifications to show an alert/badge/sound and also download something in the background, you must have both "remote notifications" and "push notifications" enabled + set content-available to 1.
(THIRD OPTION)
{
"aps" : {
"content-available" : 1
"alert" : "You got your emails.",
"badge" : 9,
"sound" : "bingbong.aiff"
},
"acme1" : "bar",
"acme2" : 42
}
This moment from WWDC video mentions the 👆
To Quote the Apple Engineer:
Now, you can in a user remote notification, you can set the same
content available flag that you set in silent notifications, and that
allows your app to have some time to download the content or update
the content that it wants to be displayed so that when the user taps
on the notification, your content is available. And the user sees what
it does. This is a way to have a silent notification inside a user
notifications like a summary.
Notifications and iOS Application life-cycle
I'm confused about remote notifications. I thought whenever I get a notification, my app becomes active in the background and downloads something. Can you explain?
e.g. at this moment:
Your iPhone has just received a remote notification with a body of "no sender". To receive this, WhatsApp ** doesn't** have to be running in the background, i.e., you don't need "Remote Notifications" enabled from BackgroundModes. You would still receive the notification even if your app was force-quit or suspended because the process is managed by the OS, not the WhatsApp app. However, if you want to be able to download the actual message or its image/video to WhatsApp (so that once your user opens WhatsApp, the video would be sitting there waiting for the user), well then you need your app to become active. To do so, you need content-available : 1 and implement application(_:didReceiveRemoteNotification:fetchCompletionHandler:) .
Similarly, if you disable cellular data for an app, you would still receive its notifications. However, by tapping on that notification, the user won't be able to make any network requests for that app. They would only be able to open the app.
Or as for another similar scenario, if the server/access point you're connected to has restricted access for, say, WhatsApp, it would still allow you to receive the APNs notifications. However, by tapping on that notification, the user won't be able to make any network requests for that app. They would only be able to open the app.
CAVEAT: If the app was force-quit by the user, then while you do get the notification for the above-mentioned reasons, you can't do anything to bring the app out of its terminated state automatically (even if you had content-available set to 1). None of your delegate methods would be hit. The user must open the app and only then your delegate methods will be reached.
A note on reliability and APNs architecture:
Although notifications are heavily used to deliver the actual content to the app, they are somewhat NOT designed to deliver content to the app. Rather, they are designed to notify the user that "hey something new has arrived (a 2b message or a 50kb small image, or a 10MB image or a 2 GB video). Open the app if you like. By the way, here's a small piece of it (the actual message itself if it can fit, the title of the image or a thumbnail shown in the notification, a title of the video or a thumbnail shown in the video". For more, see iOS APNs “best-effort” fallback. To repeat, you never download the 40MB attachment sent in the email. You just get notified of its existence. You send just enough (a thumbnail view of the attachment) so that the user is informed of what's new and can decide whether or not they need to open the app for more. When I was new to iOS, I thought you actually send the image/video through the push notification. You don't!
Specifically in the case of silent notifications:
When a device receives a background notification, the system may hold
and delay the delivery of the notification, which can have the
following side effects:
When the system receives a new background notification, it discards the older notification and only holds the newest one.
If something force quits or kills the app, the system discards the held notification.
If the user launches the app, the system immediately delivers the held notification.
Pushing Background Updates to Your App docs
APNs sends a limited number of silent notifications—notifications with the content-available key—per day. In addition, if the device has already exceeded its power budget for the day, silent notifications are not sent again until the power budget resets, which happens once a day. These limits are disabled when testing your app from Xcode. See Pushing Background Updates to Your App.
Troubleshooting tips for handling errors returned from ANPs
Even for remote user notifications, the user may be off of the internet and this could cause expired content or APNs could throttle you if you're sending notifications too many or too quickly. See here again
Long story short the APNs and OS are King and you're beneath it. Hence you cannot rely on it to conform to your every command. Having that said it's super reliable in the sense that you see most messaging apps utilize it successfully.
Addendum How to generate push notification certificate, .p12 or .pem and how to test it all out?
Just see this terrific answer. It has the most number of screenshots I've ever seen.
The push notification will let the user know that they receive a notification (Showing the notification popup for example). The silent notification will update, but the user won't get notified about it.
In any case, you can perform actions when notified with silent, just as if it was a push notification. The only difference is the user will not get notify with the popup notification.
With push notification:
With silent notification:
The difference is in the payload:
Push notification:
aps {
content-available: 1
alert: {...}
}
Silent notification:
aps {
content-available: 0
alert: {...}
}
And you have to set in Capabilities the background mode you choose.
Silent push notification reaches device, user does not know anything about the notification but his app gets the notification and app will be given some time to download new content and present it to the user, regardless to the state of the app (i.e. running or not running)
Remote push notification method is called only when your app is running. If app is suspended or not running, then the system wakes up or launches your app and puts it into the background running state before calling the method.
This method is intended for showing the updated content to the user.When this method is called, your app has up to 30 seconds of wall-clock time to perform the download operation and call the specified completion handler block. If the handler is not called in time, your app will be suspended.
For more technical details, you can go through this links:
Apple Notifications
Silent Notifications
I know that with the iOS Notification Service Extensions it is possibile pre-process the push notifications.
I'm searching for a procedure that allow me to skip the push notification is a condition is verified.
For example if the push is not updated anymore I want avoid to disturb the user.
Is it possible with Notification Service Extensions, or other? I've already tried setting the body to empty string but the modify is discarded.
Thanks
When you receive a notification via the Notification Service Extension, you must present a notification to the user. You cannot cancel/skip it. The best you can do is setting notificationContent.sound = nil, which will silence the notification, while still presenting the banner.
Another option is to use Silent Push Notifications, so you can pre-process it and decide wether you want to show a notification or not: then use UserNotifications to present a local notification.
When I read Apple Docs, they mention 3 types of notification: local, remote, and silent.
Local notification can be inferred from its name, that is sent by the app locally.
However, what is the difference between the other two types?
EDIT: While this answer is fully applicable, there are some additions (not changes) to notifications in iOS 12. I highly recommend watching WWDC 2018: What’s New in User Notifications and read this amazing and must read article.
Main changes are:
grouped notifications along with summary format
provisional notifications ie show notifications directly in notification center without user permission
critical notifications which ignore 'do not disturb' or 'mute'
ability to interact with the notifications in the extensions
ability to completely reset or update actions
ability to deeplink into app's notification Settings from phone's Notification Center
IMPORTANT NOTE: Not sure since when but from the Apple docs, the 'silent notification' has been renamed to 'background notification'
There are too many settings that need to be set right for it to work. I'll try to dissect them and make them easier to understand.
Overall, several things are important.
the overall difference between a silent and user notification
different types of user notifications
how a remote notification, i.e. the payload, is configured from your server
how to enable push notifications and remote notifications from background modes on your project
how to register your token with APNs for remote and silent notifications and APNs architecture
how to request permission for user notifications
enabling 'background app refresh' and 'notifications' from the device
what is content-available
understanding that the iOS is upstream to your app when it comes to receiving a remote notification
what happens when the OS receives notifications when the app has been user-terminated
A note on reliability and APNs architecture
I highly recommend everyone to watch the first 7 minutes of: WWDC 2015: What's new in Notifications. From there, the presenter mentions that there are 2 major types of notifications:
Silent Notifications
They happen in the background, hence you never see any alert/badge/sound. Things get downloaded without you knowing about them.
iOS 11 bug
See here.
iOS 11 initial releases were buggy for silent notifications. Make sure
you have the latest version for your testing, otherwise, it may not
work
User Notifications
As the name says, it has something to do with the user. That is, the user will see an alert/badge or hear a sound. It has 2 types.
Local Notifications
A Local Notification can be triggered in 3 different ways:
UNLocationNotificationTrigger:
You see an alert when you're close to a Walmart store.
UNTimeIntervalNotificationTrigger: e.g. You see an alert every 10 minutes.
UNCalendarNotificationTrigger like December 1st 1:00PM 2017.
Remote Notifications
They are similar to local notifications but they are triggered from the server, e.g. a WhatsApp message that has a From field (Mom) and a body field (I love you!).
Token registration and APNs architecture:
To receive a silent or remote notification, you need to register for a token using:
application.registerForRemoteNotifications()
👆 Registering does NOT require user permission. This makes silent notifications to become seamless. See this moment of the WWDC video
Silent notifications are enabled by default. The user does not need
to approve your -- does not give permission to your app to use them,
and you can just start using them without asking the user for
permission.
From WWDC
Remember APNs is delivered to your users by APNs and not by your server. So your iOS code must send this token to your server. So the server can associate a given device token with the user. When you want to push to a certain user, your server just tells APNs to send a payload to a specific token. What's important to understand is that your server and APNs are two different things
The flow of it looks like this:
Â
Â
server/provider sends a payload to APNs
APNs send a notification to all target devices of a given account. e.g. your iPhone, Mac could both receive notifications for emails/messages.
Then your iPhone/Mac will deliver that message to the app. APNs don't directly send messages to your app. It sends it to the device. Then the iOS sends it to your app.
For more on this see docs APNs Overview and Sending Notification Requests to APNs
To be able to show badges/alerts/sounds, you need to request permission from the user:
UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound]) { (granted, error) in
guard error == nil else {
//Display Error.. Handle Error.. etc..
return
}
if granted {
//Do stuff here..
//Register for RemoteNotifications. Your Remote Notifications can display alerts now :)
application.registerForRemoteNotifications()
}
else {
//Handle user denying permissions..
}
}
Question: Do I need to request access once for local notifications and once for remote notifications?
No. Just write the snippet above and it will request access for both remote and local.
Now let's get to the tricky part :D
Xcode Project + iPhone Settings
Do I need to enable something to receive silent notifications?
You must enable Push Notifications from your Xcode capabilities:
If you don't enable this, your app won't receive a token. And without a token, the server doesn't recognize you.
To be able to download stuff from the background, you need to enable: remote notifications from background modes.
To enable backgroundModes, you can do it either using your plist or Xcode capabilities.
The reason you can do it, either way, is because plist is closer to your code and is the old way, perhaps it's there for legacy support. Xcode capabilities is the newer, easy way.
plist:
Item 0 is just an index, it's not the key of a dictionary (something you normally see in plist), the UIBackgroundModes is an array of Strings. The strings must only come from an accepted value from the UIBackgroundModes Array.
Xcode Capabilities:
Check the Remote Notification in Xcode under background modes as below:
If you don't do any of the above, then toggling off notifications with:
will kill Remote & Local Notifications
However, if you do enable background app refresh from plist or Xcode capabilities, then even with notifications turned off for the app, you will still receive silent notifications!
If the user wants to disable silent notifications, he would have to disable both notifications and disable 'background app refresh for your app / across the system.
To disable 'background app refresh' across your system, you have to do this:
Why am I saying all this? To explain to you that settings of silent and push notifications are different for the user and the restrictions for sending them are different. For more, see this moment from the WWDC video. See here instead (the previous link was dead):
Silent notifications are enabled by default.
The user does not need to approve your does not give permission to
your app to use them, and you can just start using them without asking
the user for permission.
But silent notifications are the mechanism behind background app
refresh.
At any point you know that the user can go in settings and disable
them.
So you can't depend on them always being available.
You don't know if the user the turn them off, and you are not getting
a notification anymore.
This also means that silent notifications are delivered with the best
effort.
That means that when the notification arrives on the user's device,
the system is going to make some choices.
It's going to use different signals from the device and from the user
behavior, like power or the time of day to decide when it is a good
time to deliver the notification and launch your app.
It may try to save battery or it may try to match the user behavior
and make the content available when the user is more likely to use it.
Also see here.
CAVEAT: Even if you disable app background refresh and disable allow notifications, you can still receive silent notifications if your app is in FOREGROUND. If your app is in the background, it won't be delivered.
Do I need to enable something to receive remote notifications?
You just need to enable Push Notifications from your Xcode capabilities:
If you don't enable this, your app won't receive a token. And without a token, the server doesn't recognize you.
APNs Payload structure
Curious... Can you tell me what should my payload look like?
I highly recommend you see Apple§ documentation. It's very clear AND ALSO SEE Sending Notification Requests to APNs. Basically platform makes an HTTP/2 call to APNs and sends the desired payload. Sending the correct headers is critical otherwise your notifications are not delivered to the devices!
Thanks, but can you just tell me the important parts?
uhhmm... OK, but just so you know this is from the link I just said:
For Silent Notifications there is a single criterion:
The payload's aps dictionary must include the content-available key
with a value of 1.
Per docs you can send other fields
If there are user-visible updates that go along with the background
update, you can set the alert, sound, or badge keys in the aps
dictionary, as appropriate.
A sample payload would look like this:
{
"aps" : {
"content-available" : 1
},
"acme1" : "bar",
"acme2" : 42
}
acme1, acme2, or just some custom data! But for the aps key, you MUST follow Apple's structure, otherwise, it won't map correctly and you won't be able to read data correctly.
Note: I haven't verified this, but another engineer mentioned that if you have provisional notifications enabled then to ensure silent notifications are delivered you must include an alert field with an empty body. For example:
{
"aps" : {
"content-available" : 1,
"alert" : {
"body" : "",
},
},
}
For User Notifications:
You need an alert key inside your aps.
As an example:
{
"aps" : {
"alert" : "You got your emails.",
"badge" : 9,
"sound" : "bingbong.aiff"
},
"acme1" : "bar",
"acme2" : 42
}
There is also a third option which I will discuss further down the answer.
As for what the fixed aps and alert dictionary keys are, see these Apple docs.
OK, got it. What is content-available?
Very simple. It's just a flag that tells your app that you need to wake up and download something because I have content available for download! For more info, see this exact moment.
By default the content-available flag is not included, i.e., by default the notifications you send won't trigger application(_:didReceiveRemoteNotification:fetchCompletionHandler:) or do something in your app. It would just show the notification. If you want to wake up the app (to do something in the background), you need to include content-available and set it to 1.
§: If you're using Firebase, your payload structure and keys may be slightly different. For example, the key content-available is replaced by content_available. For more, see Firebase documentation and also here.
I know you told me that I can only download something into my app when I'm using silent notifications, but is there a way that I can also wake my app up in the background AND download something for remote notifications?
Yes, but then similar to the silent notification, you must also set the content-available flag to 1, so it would know to wake up and download something. Otherwise, it would just pop and alert/badge/sound but won't download anything.
IMPORTANT NOTES:
If your app has only silent notifications, just enable "push notifications" + "remote notifications" from capabilities and set content-available to 1 for each payload.
If your app has only remote notifications, just enable "push notifications" from capabilities. There's nothing to do for the content-available.
However, if you want your notifications to show an alert/badge/sound and also download something in the background, you must have both "remote notifications" and "push notifications" enabled + set content-available to 1.
(THIRD OPTION)
{
"aps" : {
"content-available" : 1
"alert" : "You got your emails.",
"badge" : 9,
"sound" : "bingbong.aiff"
},
"acme1" : "bar",
"acme2" : 42
}
This moment from WWDC video mentions the 👆
To Quote the Apple Engineer:
Now, you can in a user remote notification, you can set the same
content available flag that you set in silent notifications, and that
allows your app to have some time to download the content or update
the content that it wants to be displayed so that when the user taps
on the notification, your content is available. And the user sees what
it does. This is a way to have a silent notification inside a user
notifications like a summary.
Notifications and iOS Application life-cycle
I'm confused about remote notifications. I thought whenever I get a notification, my app becomes active in the background and downloads something. Can you explain?
e.g. at this moment:
Your iPhone has just received a remote notification with a body of "no sender". To receive this, WhatsApp ** doesn't** have to be running in the background, i.e., you don't need "Remote Notifications" enabled from BackgroundModes. You would still receive the notification even if your app was force-quit or suspended because the process is managed by the OS, not the WhatsApp app. However, if you want to be able to download the actual message or its image/video to WhatsApp (so that once your user opens WhatsApp, the video would be sitting there waiting for the user), well then you need your app to become active. To do so, you need content-available : 1 and implement application(_:didReceiveRemoteNotification:fetchCompletionHandler:) .
Similarly, if you disable cellular data for an app, you would still receive its notifications. However, by tapping on that notification, the user won't be able to make any network requests for that app. They would only be able to open the app.
Or as for another similar scenario, if the server/access point you're connected to has restricted access for, say, WhatsApp, it would still allow you to receive the APNs notifications. However, by tapping on that notification, the user won't be able to make any network requests for that app. They would only be able to open the app.
CAVEAT: If the app was force-quit by the user, then while you do get the notification for the above-mentioned reasons, you can't do anything to bring the app out of its terminated state automatically (even if you had content-available set to 1). None of your delegate methods would be hit. The user must open the app and only then your delegate methods will be reached.
A note on reliability and APNs architecture:
Although notifications are heavily used to deliver the actual content to the app, they are somewhat NOT designed to deliver content to the app. Rather, they are designed to notify the user that "hey something new has arrived (a 2b message or a 50kb small image, or a 10MB image or a 2 GB video). Open the app if you like. By the way, here's a small piece of it (the actual message itself if it can fit, the title of the image or a thumbnail shown in the notification, a title of the video or a thumbnail shown in the video". For more, see iOS APNs “best-effort” fallback. To repeat, you never download the 40MB attachment sent in the email. You just get notified of its existence. You send just enough (a thumbnail view of the attachment) so that the user is informed of what's new and can decide whether or not they need to open the app for more. When I was new to iOS, I thought you actually send the image/video through the push notification. You don't!
Specifically in the case of silent notifications:
When a device receives a background notification, the system may hold
and delay the delivery of the notification, which can have the
following side effects:
When the system receives a new background notification, it discards the older notification and only holds the newest one.
If something force quits or kills the app, the system discards the held notification.
If the user launches the app, the system immediately delivers the held notification.
Pushing Background Updates to Your App docs
APNs sends a limited number of silent notifications—notifications with the content-available key—per day. In addition, if the device has already exceeded its power budget for the day, silent notifications are not sent again until the power budget resets, which happens once a day. These limits are disabled when testing your app from Xcode. See Pushing Background Updates to Your App.
Troubleshooting tips for handling errors returned from ANPs
Even for remote user notifications, the user may be off of the internet and this could cause expired content or APNs could throttle you if you're sending notifications too many or too quickly. See here again
Long story short the APNs and OS are King and you're beneath it. Hence you cannot rely on it to conform to your every command. Having that said it's super reliable in the sense that you see most messaging apps utilize it successfully.
Addendum How to generate push notification certificate, .p12 or .pem and how to test it all out?
Just see this terrific answer. It has the most number of screenshots I've ever seen.
The push notification will let the user know that they receive a notification (Showing the notification popup for example). The silent notification will update, but the user won't get notified about it.
In any case, you can perform actions when notified with silent, just as if it was a push notification. The only difference is the user will not get notify with the popup notification.
With push notification:
With silent notification:
The difference is in the payload:
Push notification:
aps {
content-available: 1
alert: {...}
}
Silent notification:
aps {
content-available: 0
alert: {...}
}
And you have to set in Capabilities the background mode you choose.
Silent push notification reaches device, user does not know anything about the notification but his app gets the notification and app will be given some time to download new content and present it to the user, regardless to the state of the app (i.e. running or not running)
Remote push notification method is called only when your app is running. If app is suspended or not running, then the system wakes up or launches your app and puts it into the background running state before calling the method.
This method is intended for showing the updated content to the user.When this method is called, your app has up to 30 seconds of wall-clock time to perform the download operation and call the specified completion handler block. If the handler is not called in time, your app will be suspended.
For more technical details, you can go through this links:
Apple Notifications
Silent Notifications
When we receive a push notification while the application is in the background mode, it automatically uses aps and other parameters like Sound, Badge, Alert to generate a notification that appears on top.
What I want is to prevent that auto generated notification let it call didReceiveRemoteNotification and generate my custom local notification and display it on top and notification centre.
The reason behind this is that the message is customised according to situation which is managed locally after some data received in push notification.
I haven't tried anything, because I couldn't find any solution for this kind of scenario. I don't even know whether it is even possible or not.
Any help or other suggestion that could to solve this other way is highly appreciated.
You can have a look to iOS Silent Notifications here
But you have 2 differences cases :
1 your app is in front, the did receive remote is called, and the notification is not displayed.
2 your app is in background, and I don't think the didreceiveRemove is called.
So in the 2 situations, you will not achieve your goal. You shroud maybe try to customize the notification before sending it
Even when your App is in the background, suspended, inactive or terminated it is woken by a Silent push notification.
(Note: the only scenario when the app is not woken by silent push is when it had been killed off by the user from the control centre)
So you can send a silent push, perform whatever operations you need to perform on the data and then generate a local notification which would go in the tray.