Cannot get data using NSURLConnection with GCD - ios

Question

So I am downloading some data from a server to my ios client. The data needs to be formatted so I use NSNotification to notify the app when the data has been downloaded completely and when thats done, I format the data and then display it on the screen.
All this is cool but because of the size of the data, the screen freezes.I thought I should use GCD to push the data downloading to another thread so the UI is still responsive. When i did that, I dont seem to be downloading any data.
I have a method getTops that uses NSURLConnection to download the data. Initially, in my viewDidLoad I called this method and it worked fine but then I used GCD like so
dispatch_queue_t getItemsQ = dispatch_queue_create("get Items", NULL);
dispatch_async(getItemsQ, ^{
[self getTops];
});
And it stopped working. I know it gets to the getTops because I can see the log in the console but it never reaches the -(void)connectionDidFinishLoading:(NSURLConnection *)connection
Here is the code i used:
-(void)getTops{
Keychain *keychain = [[Keychain alloc]init];
NSString *auth_token = [keychain getAuthToken];
NSLog(#"at getTops");
topimageArray = [[NSMutableArray alloc]init];
NSURLConnection *connection;
webData = [[NSMutableData alloc]init];
NSURL *url = [[NSURL alloc]initWithString:base];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc]init];
[request setURL: url];
[request setValue:auth_token forHTTPHeaderField:#"X-AUTH-TOKEN"];
connection = [NSURLConnection connectionWithRequest:request delegate:self];
// [connection start];
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
NSLog(#"at getTops conn start");
}
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
NSLog(#"recieved response");
[webData setLength:0];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
if(data) {
NSLog(#"Appending data");
[webData appendData:data];
}
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
NSArray *response= [NSJSONSerialization JSONObjectWithData:webData options:0 error:nil];
NSLog(#"Tops full response::: %#",response);
theArray = [[NSArray alloc]initWithArray:response];
NSLog(#"DONE");
//Notify that the data is ready to be formated
[[NSNotificationCenter defaultCenter]postNotificationName:#"getTops" object:nil];
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
NSLog(#"error::::%#", error);
NSString *errormsg = error.localizedDescription;
UIAlertView *alertview = [[UIAlertView alloc]initWithTitle:#"Error" message:errormsg delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil, nil];
[alertview show];
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}
I thought maybe I should remove the [UIApplication sharedApplication].networkActivityIndicatorVisible but that didnt help
Edit:: Added NSLogs to delegate methods.
The Log that I get is
at getTops conn start
And thats it.

Answer 1

The simplest way is to use sendAsynchronousRequest:queue:completionHandler:. No delegates are necessary, just put the code from connectionDidFinishLoading: in the completion block.
Loads the data for a URL request and executes a handler block on an operation queue when the request completes or fails.
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
< your code >
}];