Detect if ios background fetch is running when app in foreground

Question

I have a background fetch that updates my local sqlite data.

If the app is also running in the foreground, I want to be able to detect if the background fetch is running in order to stop the UI attempting to load partially populated sql rows.

How can I detect if a background fetch is running?

Also, is there a better ui pattern than telling the user that they can't view the data?

Answer 1

You can check the application's state

[UIApplication sharedApplication].applicationState

There are three possible options

UIApplicationStateActive
UIApplicationStateInactive
UIApplicationStateBackground

If you need to check whether it's the UI thread, try this

if ([NSThread isMainThread])
{
    // main thread
}

Answer 2

It sounds like you should be doing your background fetch with a different managed object context from your UI managed object context.

You would save your background context when the data is consistent and available for display, and use the didSaveContextNotification to merge the changes into your UI context and update the display.

Your background fetch would not have to know anything about the UI logic. The UI logic would only have to know that it should update after the data has changed due to a merge.