returning UIImage from block - iphone

Question

I have the following code:
- (UIImage *) getPublisherLogo
{
//check the cache if the logo already exists
NSString * imageUrl = [NSString stringWithFormat:#"%#/%#&image_type=icon", self.baseUrl, self.imageUrl_];
ASIHTTPRequest * imageRequest = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:imageUrl]];
[imageRequest setTimeOutSeconds:30.0];
[imageRequest setDownloadCache:[ASIDownloadCache sharedCache]];
[imageRequest setCacheStoragePolicy:ASICachePermanentlyCacheStoragePolicy];
[imageRequest setCachePolicy:ASIAskServerIfModifiedWhenStaleCachePolicy|ASIFallbackToCacheIfLoadFailsCachePolicy];
[imageRequest setCompletionBlock:^(void){
UIImage *img = [UIImage imageWithData:[imageRequest responseData] ];
if (img){
return img;
}
}];
[imageRequest setFailedBlock:^(void){
NSLog(#"Error in pulling image for publisher %#", [[imageRequest error] userInfo]);
}];
[imageRequest startAsynchronous];
}
}
The issue is that the return value/UIImage is returned at a block. How do I avoid this?

Answer 1

You're unable to return anything from the completion block because it's returned void.
You'll probably need to create a new method like setLogo:(UIImage *)image on the object that's expecting the image to be set, and call that method from within the completion block.

Answer 2

You can place your img pointer outside the block and declare it __BLOCK and use it as a closure. But you really need to be asking yourself what do you plan to do with img, bearing in mind the call is made asynchronously. I would imagine you should make another call in the block to another method and pass in the populated image as a parameter.

Answer 3

For getting an object from the ASIHttpRequest response, I use notifications.
For example, in the calling viewController
- (void)viewDidLoad {
// Subscribe notifications
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(onGetPhoto:) name:#"getPhotoNotification" object:nil];
}
- (void)viewDidUnload {
[super viewDidUnload];
// Unsubscribe from notifications
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"getPhotoNotification" object:nil];
}
- (void)onGetPhoto:(NSNotification *)notification {
...
}
in your completion block
[[NSNotificationCenter defaultCenter] postNotificationName:#"getPhotoNotification" object:self userInfo:userInfo];
With your photo in userInfo.