Asynchronous Download of Image - ios

Question

I am trying to download an image off of a server asynchronously. After the image is downloaded and placed, I then want the app to go to the next view controller with an image view that will contain the image. Here is my code:
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"http://...../.png"]] cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:10];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:request queue:queue
completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
if ( !error ) {
image = [[UIImage alloc] initWithData:data];
if (image != NULL) {
[self performSegueWithIdentifier:#"midnight" sender:self];
}
}
NSLog(#"%#", image);
}];
}
The problem is that the next view controller will come up with nothing on it for about 10-15 seconds and then show the image and the text that is supposed to be displayed on the view controller. Is there something that I am doing wrong here?

Answer 1

This worked fine for me. I used your code, but changed the operation queue to the mainQueue, and added code to pass the image to the ImageViewController:
#import "ViewController.h"
#import "ImageViewController.h"
#interface ViewController ()
#property (strong,nonatomic) UIImage *image;
#end
#implementation ViewController
-(IBAction)downloadPic:(id)sender {
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"https://atmire.com/labs17/bitstream/handle/123456789/7618/earth-map-huge.jpg?sequence=1"]] cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:10];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
if ( !error ) {
_image = [[UIImage alloc] initWithData:data];
if (_image != NULL) {
NSLog(#"Image id: %#", _image);
NSLog(#"Image size is: %#", NSStringFromCGSize(_image.size));
[self performSegueWithIdentifier:#"midnight" sender:self];
}
}else{
NSLog(#"Error is: %#",error);
}
}];
}
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
ImageViewController *ivc = segue.destinationViewController;
ivc.receivedImage = _image;
}
In the ImageViewController, I created a property, receivedImage, and had just this code:
#interface ImageViewController ()
#property (weak,nonatomic) IBOutlet UIImageView *iv;
#end
#implementation ImageViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.iv.image = self.receivedImage;
}