That depends on the specifics of your app. There are two common approaches:
You can ask the system to resume your app in the background periodically via the background fetch mechanism.
You can use ‘silent’ push notifications, which are not displayed to the user but are instead delivered to your app.
Both approaches come with their own limitations. You can read more about them in the Background Execution section of the App Programming Guide for iOS.
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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
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