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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