Objective-C : A simple REST Json call using AFNetworking

SimpleJsonRestCall.m

-(void)actionRegister:(UIButton *)btn{
    //Yes, I know you can use dictionary, but there is a bug in AFNetworking that fails to set parameters from dictionary. So I am doing it manually here.
    NSString *paramStr = [NSString stringWithFormat:
                          @"firstname=%@"
                          "&lastname=%@"
                          "&email=%@"
                          "&username=%@"
                          "&password=%@",
                          firstname.text,
                          lastname.text,
                          email.text,
                          username.text,
                          password.text];
    NSURL *reqURL = [NSURL URLWithString:[AURLString stringByAppendingString:paramStr]];
    NSMutableURLRequest *jsonRequest = [NSMutableURLRequest requestWithURL:reqURL];
    [jsonRequest setHTTPMethod:@"POST"];
    AFJSONRequestOperation *oper = [AFJSONRequestOperation
                                    JSONRequestOperationWithRequest:jsonRequest
                                    success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
                                        [self.spinner stopAnimating];
                                        NSDictionary *reply = [NSDictionary dictionaryWithDictionary:JSON];
                                        if ([[reply valueForKey:@"success"] boolValue]){
                                            //Account creation successful
                                            UIAlertView *alrt = [[UIAlertView alloc] initWithTitle:@"Registered"
                                                                                           message:@"Your Account is successfully registered!"
                                                                                          delegate:Nil
                                                                                 cancelButtonTitle:@"OK"
                                                                                 otherButtonTitles: nil];
                                            [alrt show];
                                        }
                                        else{
                                            //Success is 'fail'
                                            NSString *msg = [reply valueForKey:@"msg"];
                                            UIAlertView *alrt = [[UIAlertView alloc] initWithTitle:@"Error" 
                                                                                           message:msg 
                                                                                          delegate:Nil 
                                                                                 cancelButtonTitle:@"OK" 
                                                                                 otherButtonTitles: nil];
                                            [alrt show];
                                        }
                                    }
                                    failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON) {
                                        //possibly some network error
                                        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Failed"
                                                                                        message:[error localizedDescription]
                                                                                       delegate:nil
                                                                              cancelButtonTitle:@"OK"
                                                                              otherButtonTitles: nil];
                                        [alert show];
                                    }];
    [oper start];
}