ios - Setting UILabel text taking longer than expected iOS7 -

in view attempt display weather related info. use

dispatch_async(dispatch_get_global_queue(dispatch_queue_priority_default, 0), ^{     make nsurl , other related things     send nsurlrequest     set 2 uilabels data     nslog(show data retrieved) }); 

for reason, see nslog line 15-45 seconds before uilabel changes new text. new obj-c , lot of code comes using tutorial dont have greatest understanding of dispatch_async method. thoughts or suggestions appreciated.

dispatch_async(dispatch_get_global_queue(dispatch_queue_priority_default, 0), ^{         nsurlresponse *response = nil;         nserror *error = nil;         nsdata *respdata = nil;         nsurlrequest *forecastrequest = [nsurlrequest requestwithurl:currentforecasturl];         respdata = [nsurlconnection sendsynchronousrequest:forecastrequest returningresponse:&response error:&error];         [_responsedata appenddata:respdata];         nslog(@"response: %@", response);         nslog(@"error: %@", error);         id json = [_responsedata yajl_json];         currentforecast = [[nsarray alloc]initwithobjects:[json objectforkey:@"temperature"],[json objectforkey:@"feelslike"],nil];          [_temperaturelabel settext:[nsstring stringwithformat:@"%@",[json objectforkey:@"temperature"]]];         [_tempdescriptionlabel settext:[nsstring stringwithformat:@"%@",[json objectforkey:@"desc"]]];         [uiview beginanimations:nil context:null];         [uiview setanimationduration:2.0];         [_tempdescriptionlabel setalpha:1];         [_temperaturelabel setalpha:1];         [uiview commitanimations];         nslog(@"done");          nslog(@"json: %@", [json yajl_jsonstringwithoptions:yajlgenoptionsbeautify indentstring:@"  "]);     }); 

dispatch_async(dispatch_get_global_queue(dispatch_queue_priority_default, 0) 

is used create background thread, user interface should updated in main thread

like this:

dispatch_async(dispatch_get_global_queue(dispatch_queue_priority_default, 0), ^{        //do stuff in background       dispatch_async(dispatch_get_main_queue(), ^{           // update ui      });  });