Question

I need help on how to keep in-app-purchase items in my application downloading when the user sleeps his iPhone, or the application enter the background mode. Does anyone have any ideas?

Answer 1

Define BackgroundTaskWithExpirationHandler in applicationDidEnterBackground: like this:

// ...
UIBackgroundTaskIdentifier bti;
// ...

- (void)applicationDidEnterBackground:(UIApplication *)application {
    bti = [application beginBackgroundTaskWithExpirationHandler:^{
        dispatch_async(dispatch_get_main_queue(), ^{
            if(bti != UIBackgroundTaskInvalid) {
                [application endBackgroundTask:bti];
                bti = UIBackgroundTaskInvalid;
            }
        });
    }];
    
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        // DO or CONTINUE RESUMED DOWNLOAD HERE
        
        dispatch_async(dispatch_get_main_queue(), ^{
            if(bti != UIBackgroundTaskInvalid) {
                [application endBackgroundTask:bti];
                bti = UIBackgroundTaskInvalid;
            }
        });
    });
}

To see how it works download sample project I made for You.

git clone
https://github.com/jacekmigacz/BTWEH.git

…and press Home Button to trigger applicationDidEnterBackground:.

Idea is to delegate your download task to another, privileged thread and keep your application in background state instead of let OS suspend it.