Geek asks and answers

IOS - the thread does not return to the main thread

I have problems with my threads. After I cross several times between two screens when the thread is busy. A thread does not execute every line. The breakpoint simply disappears when it should return to the main thread. Can someone please help me?

I disconnect the stream when unloading the view.

Thank,

- (void)fetchFeedDataIntoDocument
{
    NSString * labelString = [NSString stringWithFormat:@"Feed Fetcher %@", self.pageTitle];
    const char *label = [labelString UTF8String];

    self.fetchF = dispatch_queue_create(label, NULL);
    dispatch_async(self.fetchF, ^{

        NSArray *feeds = [FeedFetcher getDataForJson:self.pageTitle downloadBy:@"up"];

        NSDictionary *lastfeed;

        AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

        NSManagedObjectContext *context = [appDelegate getManagedObjectContext];

        if ([feeds count] > 0)
        {
            lastfeed = [feeds objectAtIndex:0];

            [FeedFetcher setLastUpdateIdToCatgorie:self.pageTitle WithId:[lastfeed objectForKey:@"id"] AndPulishDate:[lastfeed objectForKey:@"publish_up"]];
        }

        for (NSDictionary *feedInfo in feeds) {
            [Feed FeedWithInfo:feedInfo InManageObject:context];
        }

        NSError *error = nil;

        [context save:&error];

        if (error){
            NSLog(@"Error save : %@", error);}

        dispatch_async(dispatch_get_main_queue(), ^{
            [self setupFetchedResultsController];
            [self.tableView reloadData];
            [self downloadImagesForFeeds:feeds];
        });

    });
+3
source share
4 answers

You access managedObjectContext from another thread from which it was created. This is rule number 1 for data processing.

MOC . MOC, Xcode, concurrency. executeBlock. MOC . . - , .

, MOC. ( - )...

NSManagedObjectContext *moc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
moc.parentContext = appDelegate.managedObjectContext;
[moc performBlock:^{
    // Go get your remote data and whatever you want to do

    // Calling save on this MOC will push the data up into the "main" MOC
    // (though it is now in the main MOC it has not been saved to the store).
    [moc save:&error];
}];

- ...

- (void)fetchFeedDataIntoDocument
{
    NSString * labelString = [NSString stringWithFormat:@"Feed Fetcher %@", self.pageTitle];
    const char *label = [labelString UTF8String];

    AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
    NSManagedObjectContext *mainContext = [appDelegate getManagedObjectContext];
    NSManagedObjectContext *context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
    context.parentContext = mainContext;
    [context performBlock:^{    
        NSArray *feeds = [FeedFetcher getDataForJson:self.pageTitle downloadBy:@"up"];

        NSDictionary *lastfeed;


        if ([feeds count] > 0)
        {
            lastfeed = [feeds objectAtIndex:0];

            [FeedFetcher setLastUpdateIdToCatgorie:self.pageTitle WithId:[lastfeed objectForKey:@"id"] AndPulishDate:[lastfeed objectForKey:@"publish_up"]];
        }

        for (NSDictionary *feedInfo in feeds) {
            [Feed FeedWithInfo:feedInfo InManageObject:context];
        }

        NSError *error = nil;

        [context save:&error];

        if (error){
            NSLog(@"Error save : %@", error);}
DO you really want to continue on error?
        dispatch_async(dispatch_get_main_queue(), ^{
            // Data has been pushed into main context from the background
            // but it still needs to be saved to store...
            // Do not forget to perform error handling...
            NSError *error = nil;
            [mainContext save:&error];
            [self setupFetchedResultsController];
            [self.tableView reloadData];
            [self downloadImagesForFeeds:feeds];
        });

    });

, Xcode MOC, init, NSConfinementConcurrencyType. MainConcurrency - , .

...

    __managedObjectContext = [[NSManagedObjectContext alloc] init];

...

    __managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];

MOC "", executeBlock.

+11

..

   dispatch_queue_t queue1 = dispatch_queue_create("com.MyApp.AppTask",NULL);
   dispatch_queue_t main = dispatch_get_main_queue();
   dispatch_async(queue1, 
               ^{
                   dispatch_async(main, 
                                  ^{
                                      [self setupFetchedResultsController];
                                      [self.tableView reloadData];
                                      [self downloadImagesForFeeds:feeds];

                                  });

               });

,

0

how about this ...

-(void)functionToCallFetch {

     [self performSelectorInBackground:@selector(fetchFeedDataIntoDocument) withObject:nil];

} 

- (void)fetchFeedDataIntoDocument
{

     NSArray *feeds = [FeedFetcher getDataForJson:self.pageTitle downloadBy:@"up"];

        NSDictionary *lastfeed;

        AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

        NSManagedObjectContext *context = [appDelegate getManagedObjectContext];

        if ([feeds count] > 0)
        {
            lastfeed = [feeds objectAtIndex:0];

            [FeedFetcher setLastUpdateIdToCatgorie:self.pageTitle WithId:[lastfeed objectForKey:@"id"] AndPulishDate:[lastfeed objectForKey:@"publish_up"]];
        }

        for (NSDictionary *feedInfo in feeds) {
            [Feed FeedWithInfo:feedInfo InManageObject:context];
        }

        NSError *error = nil;

        [context save:&error];

        if (error){
            NSLog(@"Error save : %@", error);}

        //dispatch_async(dispatch_get_main_queue(), ^{
        //    [self setupFetchedResultsController];
        //    [self.tableView reloadData];
        //    [self downloadImagesForFeeds:feeds];
        //});
        [self performSelectorOnMainThread:@selector(setupFetchedResultsController) withObject:nil waitUntilDone:NO];
        [self.tableView performSelectorOnMainThread:@selector(reloadData) withObject:nil waitUntilDone:NO];
        [self performSelectorOnMainThread:@selector(downloadImagesForFeeds:) withObject:feeds waitUntilDone:NO];


}

Maybe this will work better?

0
source

You tried to create a method such as:

- (void)methodToBePerformedOnMainThread{
        [self setupFetchedResultsController];
        [self.tableView reloadData];
        [self downloadImagesForFeeds:feeds];
}

and name him

[self performSelectorOnMainThread:@selector(methodToBePerformedOnMainThread) withObject:nil waitUntilDone:NO];

in the end fetchFeedDataIntoDocument

Edit:

Have you tried to wrap it with NSOperationQueue instead of dispatch_queue?

Like:

NSOperationQueue *operationQueue = [NSOperationQueue new];

NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(fetchFeedDataIntoDocument) object:nil];

if(operation != nil){
    [operationQueue addOperation:operation];
0
source

More articles:


All Articles