HTTP call runs first time but then waits forever - ios

Question

I'm using SDWebImage to load images asynchronously. I want to combine comments and photos in a dictionary like below:
- (NSArray *) fetchPhotos:(NSArray *) requestedPhotoArray
{
NSMutableArray *photos;
UIImageView *imageview;
for (requestedPhoto in requestedPhotoArray) {
[imageview setImageWithURL:[NSURL URLWithString: requestedPhoto.url]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
NSDictionary *parameters = #{ #"function":GET_COMMENT,
#"photoId":requestedPhoto.photoID,
}
NSArray *comments = [[self.communicator sharedInstance] HTTPRequestWithParams:parameters];
Photo *photo = [Photo photoWithDictionary:
#{#"imageView": imageview,
#"comments" : comments,
}];
[photos addObject:photo];
}
return photos;
}
But fetchPhotos function makes one http call and waits forever and then nothing returns.
fetchPhotos is called like below (simplified version):
NSDictionary *parameters = #{#"function":GET_PHOTO_INFO_ARRAY,
#"userid":3,
#"pageid":99,
}
dispatch_async(dispatch_get_global_queue(0, 0), ^{
requestedPhotosInfoArray = [[self.communicator sharedInstance] HTTPRequestWithParams:parameters];
dispatch_async(dispatch_get_main_queue(), ^{
[self fetchPhotos: requestedPhotosInfoArray];
}
communicator:HTTPRequestWithParams do a HTTP request like below
...
__block id result;
dispatch_queue_t queue = dispatch_queue_create("my_queue", 0);
dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
dispatch_async( queue, ^{
[manager POST:url parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {
result = responseObject;
dispatch_semaphore_signal(semaphore);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
result = error;
dispatch_semaphore_signal(semaphore);
}
];
});
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
return result;
Any idea why fetchPhotos only returns first data and waits forever?
UPDATE:
I realised that it waits in
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
then I add a async dispatch queue in fetchPhotos
for (requestedPhoto in requestedPhotoArray) {
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(queue, ^{
[imageview setImageWithURL:[NSURL URLWithString: requestedPhoto.url]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
NSDictionary *parameters = #{ #"function":GET_COMMENT,
#"photoId":requestedPhoto.photoID,
}
NSArray *comments = [[self.communicator sharedInstance] HTTPRequestWithParams:parameters];
....
It's not waiting forever now but it doesn't make a http call.

Answer 1

I used block callback instead of semaphores
dispatch_async( queue, ^{
[manager POST:url parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {
if (success) {
success(responseObject);
}
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
if (failure) {
failure(error);
}
}
];
});