Parse Query not returning when iOS app is in background, triggered by Background Fetch

Question

Using a Background Fetch we trigger a method

- (void)sendPush:(SPUserInfo *)userInfo {

    PFQuery *findUserQuery = [PFUser query];
    [findUserQuery whereKey:@"objectId" equalTo:userInfo.userID];
    [findUserQuery findObjectsInBackgroundWithBlock:^(NSArray* arr, NSError* err) {
        if (err) {
            MLog(@"Error Finding User to Spark: %@", err.description);
        }
        else {
            if (arr.count) {
                MLog(@"User found");
                PFObject *spark = [PFObject objectWithClassName:kSparkClassName];

                [...]

                [spark saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
                    if (!error) {
                        //save
                        // send push through Parse

                        [...]
                        PFPush *push = [PFPush push];
                        NSString *channel = [NSString stringWithFormat:@"u_%@", receiver.objectId];
                        [push setChannels:@[channel]];
                        [push setData:data];
                        [push sendPushInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
                            if (nil == error) {
                                MLog(@"Push success");
                                //do the stuff
                                [self.queueSendingSpark removeObject:userInfo];
                                [self saveSendingSparkQueue];
                            }
                            else {
                                MLog(@"Push Error : %@", error.description);
                            }
                        }];

                    }
                    else {
                        MLog(@"Spark is not saved on parse | %@", error);
                    }}];
            }
            else {
                MLog(@"ZERO Users");
            }
        }
    }];
}

This is all fine and dandy if the app is running in the foreground or if the phone is awake. But when the iPhone is locked/asleep, the findObjectsInBackgroundWithBlock never returns any data.

Is this expected behaviour? Is there a way to ensure this query, and others, are returning as normal when a device is asleep?

Answer 1

So theres a property that you can use to handle this...

@property (nonatomic, assign) UIBackgroundTaskIdentifier fileUploadBackgroundTaskId;

Within your init method set the property like so:

self.fileUploadBackgroundTaskId = UIBackgroundTaskInvalid;

Set the value when needed

// Request a background execution task to allow us to finish uploading the photo even if the app is backgrounded
self.fileUploadBackgroundTaskId = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
    [[UIApplication sharedApplication] endBackgroundTask:self.fileUploadBackgroundTaskId];
}];

Run your query, then when the query is finished...

[[UIApplication sharedApplication] endBackgroundTask:self.fileUploadBackgroundTaskId];