Best practice to use AFNetworking - ios

Question

I'm not sure if this is a question with a obvious answer but i haven't been able to find any.
I'm using AFNetworking to connect with my REST server.
I'm doing basic task like uploading and downloading images, posting and getting json etc etc.
What is the best practice to update UI when somethings changes. If for example have successfully downloadet the profile picture and need to change the image inside a tableview.
I only have 1 class that uses AFNetworking my APIConnector
APIConnector.h
#interface APIConnector : NSObject
-(void)downloadClientImageToSystem:(NSString *)imageURL;
#end
APIConnector.m
-(void)downloadClientImageToSystem:(NSString *)imageURL{
//setup
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];
//Set url
NSURL *URL = [NSURL URLWithString:[NSString stringWithFormat:#"%#%#",backendURL,imageURL]];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
//Create a download task
NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request progress:nil destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) {
NSURL *documentsDirectoryURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil];
NSString *filename = [NSString stringWithFormat:#"%#.jpeg",[[imageURL componentsSeparatedByString:#"&imgIndex="] lastObject]];
return [documentsDirectoryURL URLByAppendingPathComponent:filename];
} completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error)
{
if (error) {
NSLog(#"there was an error downloading profile image");
[[NSNotificationCenter defaultCenter] postNotificationName:DLImageFail object:self];
}
else{
NSLog(#"File downloaded to: %#", filePath);
[[NSNotificationCenter defaultCenter] postNotificationName:DLImageSucces object:self];
}
}];
[downloadTask resume];
}
As you can see this currently is using NSNotificationCenter but is this the best solution? I've been reading about Delegates and blocks and it all just seems about loose. Should i implement AFNetworking inside the classes that needs it, like the class where i try to update my tableview?
Thanks :)
Extra code example
-(void)executePostForURL:(NSString *)url dictionary:(NSDictionary *)dict success:(SuccessBlock)success failure:(FailureBlock)failure{
[httpManager POST:url parameters:dict progress:nil
success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
//somehow i need to return [responseObject valueForKey:#"updateLabelString"];
}
failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
}];
}
I'm trying to call this in viewdidload. This is of course just pseudo code and doesn't work, how do i parse the [responseObject valueForKey#"updateLabelString"] value into my labelToUpdate.text?
-(void)viewDidLoad{
NSDictionary *dicToSendToServer;
UILabel *labelToUpdate = #"temp text";
[apicon executePostForURL:#"serverurl" dictionary:dicToSendToServer success:^(NSString *test){
labelToUpdate.text = test;
}failure:nil];
}

Answer 1

I would declare it like this:
- (void)executePostForURL:(NSString *)url dictionary:(NSDictionary *)dict success:(void (^)(id objectYouRequested))success failure:(void (^)(NSError *error))failure;
I also like to use typedef to avoid some of the block syntax. I typically define the following:
typedef void (^SuccessBlock)(id result);
typedef void (^MySubclassedObjectSuccessBlock)(SubclassedObject *object);
typedef void (^FailureBlock)(NSError *error);
This then simplifies the method declaration above to:
- (void)executePostForURL:(NSString *)url dictionary:(NSDictionary *)dict success:(SuccessBlock)success failure:(FailureBlock)failure;