iOS Interview: Background Fetch || Background Task

A background task in iOS is a piece of code that is executed while an app is in the background (that is, while the app is not actively being used). There are several ways to implement background tasks in an iOS app, depending on the specific needs of the task. Some options include:

1. Background fetch: This feature of the iOS operating system allows an app to fetch new data or perform other tasks in the background when the app is not actively being used. To implement background fetch, you need to enable the “Background fetch” capability in the app’s Xcode project, and implement the application(_:performFetchWithCompletionHandler:) method in the app's UIApplicationDelegate.
2. Background tasks: The BGTaskScheduler framework allows you to schedule background tasks that are executed when the app is in the background. You can use this framework to schedule tasks to run at specific intervals or at specific times, or you can register for specific events that trigger the task.

Let’s Discuss Background Fetch in this Article.

To implement background fetch in an iOS app, you need to do the following:

1. Enable the “Background fetch” capability in the app’s Xcode project. To do this, open the project’s “Signing & Capabilities” tab, and turn on the “Background Modes” option. Then, check the “Background fetch” checkbox.

2. In the app’s UIApplicationDelegate, implement the application(_:performFetchWithCompletionHandler:) method. This method is called by the system when it wants to fetch new data for the app.

func application(_ application: UIApplication, performFetchWithCompletionHandler completionhandler: @escaping (UIBackgroundFetchResult) -> Void) {
    // Perform the background fetch here.
    // When the fetch is complete, call the completion handler with the appropriate UIBackgroundFetchResult value.
    completionHandler(.newData)
}

3. In the performFetchWithCompletionHandler method, perform the desired background task (such as fetching new data from a server). Be sure to call the completion handler when the task is finished, passing in the UIBackgroundFetchResult value that indicates the result of the fetch.

It’s important to note that iOS places strict limits on the amount of time that an app can spend executing code in the background, and apps that exceed these limits may be terminated. Therefore, it’s important to design background tasks to be as efficient as possible and to only perform the necessary work while in the background.

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