Background fetch and refresh completed after viewDidLoad in iOS 10 - ios

Question

I'm trying to implement background fetch as well as refresh in iOS 10.
I'm using XML parsing to parse the data and then storing it in a file in the document's directory. For parsing XML I'm using a custom class (XMLParser) that confirms the NSXMLParserDelegate protocol.
The background fetch works fine. But I'm having problems in displaying the refreshed data, both when I click on the refresh button as well as in viewDidLoad.
I'm calling the refreshData method in viewDidLoad.
Here's how far I've gotten.
AppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
//--Set background fetch--//
[application setMinimumBackgroundFetchInterval:UIApplicationBackgroundFetchIntervalMinimum];
}
...
#pragma mark Background data fetch methods
-(void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler{
NSDate *fetchStart = [NSDate date];
ArtsViewController *artsViewController = (ArtsViewController *)self.window.rootViewController;
[artsViewController fetchNewDataWithCompletionHandler:^(UIBackgroundFetchResult result) {
completionHandler(result);
NSDate *fetchEnd = [NSDate date];
NSTimeInterval timeElapsed = [fetchEnd timeIntervalSinceDate:fetchStart];
NSLog(#"Background Fetch Duration: %f seconds", timeElapsed);
}];
}
ArtsViewController.h
#interface ArtsViewController : UIViewController <UIPageViewControllerDataSource>
#property BOOL newsAvailable;
-(void)fetchNewDataWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler; // No problems here
#end
ArtsViewcontroller.m
#interface ArtsViewController ()
#property (nonatomic, strong) NSArray *arrNewsData;
-(void)refreshData;
-(void)performNewFetchedDataActionsWithDataArray:(NSArray *)dataArray;
#end
...
#implementation ArtsViewController
- (void)viewDidLoad {
[super viewDidLoad];
[self refreshData];
//--Load the file that saves news--//
[self loadNews];
if (_newsAvailable == YES)
{
[self setupPageViewController];
}
else
{
[self showNoNewsMessage];
}
}
...
#pragma mark Data Fetch methods
-(void)refreshData{
XMLParser *xmlParser = [[XMLParser alloc] initWithXMLURLString:ArtsNewsFeed];
[xmlParser startParsingWithCompletionHandler:^(BOOL success, NSArray *dataArray, NSError *error) {
if (success) {
[self performNewFetchedDataActionsWithDataArray:dataArray];
}
else{
NSLog(#"%#", [error localizedDescription]);
}
}];
}
-(void)performNewFetchedDataActionsWithDataArray:(NSArray *)dataArray{
// 1. Initialize the arrNewsData array with the parsed data array.
if (self.arrNewsData != nil) {
self.arrNewsData = nil;
}
self.arrNewsData = [[NSArray alloc] initWithArray:dataArray];
// 2. Write the file and reload the view.
NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString * docDirectory = [paths objectAtIndex:0];
NSString * newsFilePath = [NSString stringWithFormat:#"%#",[docDirectory stringByAppendingPathComponent:#"arts2"]]; // NewsFile
if (![self.arrNewsData writeToFile:newsFilePath atomically:YES]) {
_newsAvailable = NO;
NSLog(#"Couldn't save data.");
}
else
{
_newsAvailable = YES;
NSLog(#"Saved data.");
[self viewWillAppear:YES];
}
}
-(void)fetchNewDataWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler{
XMLParser *xmlParser = [[XMLParser alloc] initWithXMLURLString:ArtsNewsFeed];
[xmlParser startParsingWithCompletionHandler:^(BOOL success, NSArray *dataArray, NSError *error) {
if (success) {
NSDictionary *latestDataDict = [dataArray objectAtIndex:0];
NSString *latestTitle = [latestDataDict objectForKey:#"title"];
NSDictionary *existingDataDict = [self.arrNewsData objectAtIndex:0];
NSString *existingTitle = [existingDataDict objectForKey:#"title"];
if ([latestTitle isEqualToString:existingTitle]) {
completionHandler(UIBackgroundFetchResultNoData);
NSLog(#"No new data found.");
}
else{
[self performNewFetchedDataActionsWithDataArray:dataArray];
completionHandler(UIBackgroundFetchResultNewData);
NSLog(#"New data was fetched.");
}
}
else{
completionHandler(UIBackgroundFetchResultFailed);
NSLog(#"Failed to fetch new data.");
}
}];
}
...
#pragma mark IBActions
- (IBAction)reloadNews:(UIBarButtonItem *)sender
{
[self viewDidLoad];
}
I've debugged the application and found that after viewDidLoad
completes execution, the data file is written but the view isn't
updated. I've also tried calling the refreshData method in the main
thread, but there's no change.
after viewDidLoad is complete the showNoNewNews method is called.
I'm suspecting that my logic isn't wrong but implementation is. Threads at play here..
Any help would be appreciated.
Update:
Hope this helps those with similar problems...
I moved the logic of viewDidLoad to a different method, called the method for the first time in viewDidLoad and again in refreshData, after
[self performNewFetchedDataActionsWithDataArray:dataArray];