iphone - Handling try catch -

my project service oriented , comes services.i m loading data in uilabel's,tableviews etc.when particular text doesn't come service dont want show null there ,neither display view.so want redirect other view displays error image.but @try ,@catch not working.

-(void)viewdidload {   //activity indicator code   [self performselector:@selector(threadstartanimating) withobject:nil afterdelay:0.1];    nsstring *name=[nsstring stringwithformat:@"%@", self.provname];   cgsize constraint1 = cgsizemake(250, 2000.0f);   cgsize size1 = [name sizewithfont: [uifont fontwithname:@"helvetica-bold" size:18] constrainedtosize:constraint1 linebreakmode:uilinebreakmodewordwrap];   self. pname =[[uilabel alloc] init];   @try {     if([name length]>0     {       self.pname.text=[nsstring stringwithformat:@"%@" ,name];     }     else     {       nsexception *exception = [nsexception                                   exceptionwithname:@""                                   reason:@""                                   userinfo:nil];       @throw exception;     }    }    @catch (nsexception *exception) {     errorview *errorview=[[errorview alloc]initwithnibname:@"errorview" bundle:nil];     if([[[uidevice currentdevice]systemversion]floatvalue]<5.0)     {       [self presentmodalviewcontroller:errorview animated:no];     }     else     {       [self presentviewcontroller:errorview animated:no completion:nil];     }     [errorview release];   } }  - (void) threadstartanimating {    //other code  } 

but when text length 0 not redirected errorview.instead rest of code in current view being executed.

i couldn't understand m going wrong?