ios - Delegates and Datasource methods not called -

is there possible way call delegates , datasource inside grand central dispatch main_queue?

please help. if these delegates , datasource aren't called, images not displayed!

here code:

messagewebservice = [[messagewebservices alloc]init];     tempbo = [[messagebo alloc]init];     tempbo.messageid = self.messageid;     dispatch_async(webservicebackgroundqueue, ^(void){          tempbo = [messagewebservice getdetails:tempbo];         dispatch_async(dispatch_get_main_queue(), ^          {               if (!tempbo.isexception)              {                  self.subjects.text = tempbo.subject;                  self.content.text = tempbo.messageli;                  self.usernmae.text = tempbo.usernmae;                  self.creadate.text = tempbo.creationdate;                  self.phonenumb.text = tempbo.phonenumber;                  self.email.text = tempbo.email;                  self.amount.text = [nsstring stringwithformat:@"$ %@",tempbo.priceamount];                  self.imagedata = [nsdata datawithcontentsofurl:[nsurl urlwithstring:tempbo.imageurl]];                  self.img = [uiimage imagewithdata:self.imagedata];                  if(self.img)                  {                      [imagearray addobject:self.img];                  }                  else                  {                      [imagearray addobject:[uiimage imagenamed:@"no_photo.png"]];                  }                  hflowview.delegate = self;                  hflowview.datasource = self;                  hflowview.pagecontrol = hpagecontrol;                }            });     }); 

you cannot directly call delegate / datasource method, can call supporting methods trigger delegate or data source methods. eg. table view - if call reload table view, data source , delegate methods associated reload table called.

but in case of gcd, if respective class's object in scope, reflect change. or else of no use.

please provide details of exact scenario / code can guid more accurately.