why I can't use background mode in my app in swift 3?

Question

I want to use background mode in my app so in the capabilities I ticked background fetch and notification But The problem is that just in the simulator every things are ok and in the real iPhone the app will freeze in the background

Answer 1

You can't fetch the the latest content from a server in background mode as Apple only allowed to fetch content in specific reasons eg.

• Implementing Long-Running Tasks

• For tasks that require more execution time to implement, you must request specific permissions to run them in the background without their being suspended. In iOS, only specific app types are allowed to run in the background:

  • Apps that play audible content to the user while in the background, such as a music player app
  • Apps that record audio content while in the background
  • Apps that keep users informed of their location at all times, such as a navigation app
  • Apps that support Voice over Internet Protocol (VoIP)
  • Apps that need to download and process new content regularly
  • Apps that receive regular updates from external accessories

Apps that implement these services must declare the services they support and use system frameworks to implement the relevant aspects of those services. Declaring the services lets the system know which services you use, but in some cases it is the system frameworks that actually prevent your application from being suspended.

Instead of these you can fetch the content from server in short period of time eg. 1-2 mins depending of cpu usage

func doUpdate() {
    DispatchQueue.global(qos: .default).async(execute: {() -> Void in
        self.beginBackgroundUpdateTask()
        var response: URLResponse? = nil
        var error: Error? = nil
        let responseData: Data? = try? NSURLConnection.sendSynchronousRequest(request, returningResponse: response)
        // Do something with the result
        self.endBackgroundUpdateTask()
    })
}

func beginBackgroundUpdateTask() {
    backgroundUpdateTask = UIApplication.shared.beginBackgroundTask(withExpirationHandler: {() -> Void in
        self.endBackgroundUpdateTask()
    })
}

func endBackgroundUpdateTask() {
    UIApplication.shared.endBackgroundTask(backgroundUpdateTask)
    backgroundUpdateTask = UIBackgroundTaskInvalid
}