How to check when connectionDidFinishLoading finishes - ios

Question

I have set up a simple Objective-C class in my iOS app which has one simple task, to download a JSON file, parse it and then pass back a NSString which contains a variable parsed from the downloaded JSON file.
The problem I have is that I am calling this class from another class and this all works great however I need to pass back the NSString to the class from which I am calling it from.
The problem is that the method passes back the empty NSString BEFORE connectionDidFinishLoading happens.... And so the NSString never gets assigned a string......
I have setup a while loop in my method but it doesn't really work.....
here is my code:
-(NSString *)get_user_icon:(NSString *)YT_ID {
// Set BOOL to 0 for initial setup.
icon_check = 0;
NSString *url_YT = [NSString stringWithFormat:YOUT_profile_part_2, YT_ID];
dispatch_queue_t downloadQueue = dispatch_queue_create("Icon downloader YouTube", NULL);
dispatch_async(downloadQueue, ^{
dispatch_async(dispatch_get_main_queue(), ^{
NSURLRequest *theRequest_YT = [NSURLRequest requestWithURL:[NSURL URLWithString:url_YT]];
NSURLConnection *theConnection_YT = [[NSURLConnection alloc] initWithRequest:theRequest_YT delegate:self];
if (theConnection_YT) {
YT_JSON_FEED = [[NSMutableData alloc] init];
NSLog(#"Respoce happening...");
}
else {
NSLog(#"failed");
}
});
});
while (icon_check == 0) {
NSLog(#"Wait");
}
return icon_url;
}
/// Data loading ///
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
[YT_JSON_FEED setLength:0];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[YT_JSON_FEED appendData:data];
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
NSString *msg = [NSString stringWithFormat:#"Failed: %#", [error description]];
NSLog(#"%#",msg);
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection {
NSError *myError = nil;
NSDictionary *feed = [NSJSONSerialization JSONObjectWithData:YT_JSON_FEED options:NSJSONReadingMutableLeaves error:&myError];
icon_url = [[[[[feed objectForKey:#"items"] valueForKey:#"snippet"] valueForKey:#"thumbnails"] valueForKey:#"default"] valueForKey:#"url"];
icon_check = 1;
}

Answer 1

For a synchronous request (blocking until there is something to return), use NSURLConnection's sendSynchronousRequest:returningResponse:error: instead. Like so:
-(NSString *)get_user_icon:(NSString *)YT_ID {
NSString *url_YT = [NSString stringWithFormat:YOUT_profile_part_2, YT_ID];
NSURLRequest *theRequest_YT = [NSURLRequest requestWithURL:[NSURL URLWithString:url_YT]];
NSURLResponse* response = nil;
NSError* error = nil;
NSData* data = [NSURLConnection sendSynchronousRequest:theRequest_YT returningResponse:&response error:&error];
//Check response and error for possible errors here.
//If no errors.
NSDictionary *feed = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:&myError];
icon_url = [[[[[feed objectForKey:#"items"] valueForKey:#"snippet"] valueForKey:#"thumbnails"] valueForKey:#"default"] valueForKey:#"url"];
return icon_url;
}
However this is not recommended. You need to change your API to be asynchronous. Either delegate-based, but more preferably, using block-based API.