Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

General Discussion

iOS Development

It looks like we've written a bug. When we set our image on the image view, it's not working quite right. Fix this by setting the image on the image view using the main queue.

import "AwesomeViewController.h"

@implementation AwesomeViewController

  • (void)viewDidLoad { [super viewDidLoad];

    NSURL *url = [NSURL URLWithString:@"http://blog.teamtreehouse.com/wp-content/themes/treehouse/images/logo-blog2x.png"];

    NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url]; NSURLSession *session = [NSURLSession sharedSession];

    NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:request completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) { NSData *data = [[NSData alloc] initWithContentsOfURL:location]; UIImage *image = [[UIImage alloc] initWithData:data];

    self.imageView.image = image;


    [task resume]; }


Whats wrong with this code?

1 Answer

Stone Preston
Stone Preston
42,016 Points

The problem is that any updates to the UI will need to be called on the main thread (as opposed to a background thread which is what is currently happening). you can do that like so

dispatch_async(dispatch_get_main_queue(), ^{
   // do any updates to UI here such as setting an image views image