The essential purpose of both local and remote notifications is to enable an app to inform its users that it has something for them.
Local notifications are scheduled by an app and delivered on the same device.
Remote notifications, also known as push notifications, are sent by your server to the Apple Push Notification service, which pushes the notification to devices.
Local and Remote Notifications Appear the Same to Users
Users can get notified in the following ways:
An onscreen alert or banner
A badge on the app’s icon
A sound that accompanies an alert, banner, or badge
When your app is frontmost, UIKit delivers local and remote notifications directly to your app delegate object without displaying any system UI. UIKit calls the application:didReceiveLocalNotification: method for incoming local notifications and the application:didReceiveRemoteNotification:fetchCompletionHandler: method for incoming remote notifications. Use the provided notification dictionary to update your app accordingly. Because your app is running, you can incorporate the notification data quietly or update your user interface and let the user know that new information is available.
The remote notification
Each remote notification includes a payload. The payload contains information about how the system should alert the user as well as any custom data you provide. The maximum size allowed for a notification payload depends on which provider API you employ. When using the HTTP/2 provider API, maximum payload size is 4096 bytes. Using the legacy binary interface, maximum payload size is 2048 bytes. Apple Push Notification service (APNs) refuses any notification that exceeds the maximum size.
Keys and values of the aps dictionary
Key
Value type
Comment
alert
string or dictionary
If this property is included, the system displays a standard alert or a banner, based on the user’s setting.
badge
number
The number to display as the badge of the app icon.
sound
string
The name of a sound file in the app bundle or in the Library/Sounds folder of the app’s data container.
content-available
number
Provide this key with a value of 1 to indicate that new content is available. Including this key and value means that when your app is launched in the background or resumed, application:didReceiveRemoteNotification:fetchCompletionHandler: is called.
category
string
Provide this key with a string value that represents the identifier property of the UIMutableUserNotificationCategory object you created to define custom actions. To learn more about using custom actions.
Child properties of the alert property
Key
Value type
Comment
title
string
A short string describing the purpose of the notification.
body
string
The text of the alert message.
title-loc-key
string or null
The key to a title string in the Localizable.strings file for the current localization. The key string can be formatted with %@ and %n$@ specifiers to take the variables specified in the title-loc-args array.
title-loc-args
array of strings or null
Variable string values to appear in place of the format specifiers in title-loc-key.
action-loc-key
string or null
If a string is specified, the system displays an alert that includes the Close and View buttons. The string is used as a key to get a localized string in the current localization to use for the right button’s title instead of “View”.
loc-key
string
A key to an alert-message string in a Localizable.strings file for the current localization (which is set by the user’s language preference). The key string can be formatted with %@ and %n$@ specifiers to take the variables specified in the loc-args array.
loc-args
array of strings
Variable string values to appear in place of the format specifiers in loc-key.
launch-image
string
The filename of an image file in the app bundle, with or without the filename extension.
