Periodic background synchronization

ios swift3 background-process synchronisation
Mulgard picture Mulgard · Oct 30, 2016 · Viewed 7.9k times · Source

Im quite new to iOS programming and now want to implement a periodic background synchronization to synchronize my server data with client data. What I want to achieve is comparable with Androids SyncAdapter where you can define a time interval (for example each 30 minutes) and the system will trigger the defined task automatically in the background.

Until now I could not find such mechanism for Swift 3.0 so I need to ask if somone has experience or some hints for me how I can achieve this.

What I want to do sounds quite simple:

When the app starts for the first time the app should setup a sync manager which automatically triggers a background task every 30 minutes. The background task is responsible to synchronize server and client data (using Alamofire).

How can I do that?

Answer

shallowThought picture shallowThought · Oct 30, 2016

There is an iOS feature called BackgroundFetch, which you can set up for

regularly downloads and processes small amounts of content from the network

You can setup a minimumBackgroundFetchInterval.

In contrast to the mentioned Android feature, this interval is not guaranteed though.

The OS does some heuristic in a blackbox. It rewards you for using a "reasonable" (to the OS) CPU time/ power consumption and also for being used often by the user. On the other hand you get punished for draining the battery or (even worse) never being used/opened by the user.

See: Apple Sample and Apple Docs

Update: Since iOS13, BackgroundFetchis deprecated.

There is a similar, new API named BGTask, BGAppRefreshTask is the equivalent to deprecated BackgroundFetch.

See Apple Docs

Alternatively, depending on your needs, you can post a Silent (push) Notification whenever the users data changes on server side. A silent push wakes up your app without notifying the user, so you can fetch data and maybe inform the user by scheduling a local notification.

See: Apple Documentation

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