performSelector:withObject:afterDelay: not working

I was trying the below code but [self performSelector:handler withObject:data afterDelay:0] in the sync function does not call the handler1 or handler2 methods, even when I'm passing the handlers from initWithType method. The handler is not going null I have already checked that.

Can someone please tell me what is going wrong?

- (instancetype)initWithType:(NSInteger *)Handler 
    {
    switch(Handler)
    {
    case 0:
           [self sync:@selector(handler1:) withURL:SyncURL];
           break;
    case 1:
           [self sync:@selector(handler2:) withURL:SyncURL];
           break;
    default:
           break;
    }

-(void)sync : (SEL) handler withURL:(NSString *)str1{
  Reachability *reachability = [Reachability reachabilityForInternetConnection];
  NetworkStatus networkStatus = [reachability currentReachabilityStatus];

  if(networkStatus==NotReachable)
  {
      UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Message" message:@"Connection can't be established "  delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
      [alert show];
      [alert release];
      return;
  }
  else{
      NSData *poststring=[syncString dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:NO];
      NSMutableData *data = [NSMutableData data];
      [data appendData:poststring];
      NSString * postLength = [NSString stringWithFormat:@"%lu",(unsigned long)[data length]];
      NSMutableURLRequest * request =[[NSMutableURLRequest alloc] init];
      NSString *ad_user;
      NSString *ad_password;
      NSString *ad_params;
      ad_user = [[NSUserDefaults standardUserDefaults] objectForKey:@"username"];
      ad_password = [[NSUserDefaults standardUserDefaults] objectForKey:@"password"];
      NSString *password = [Utility URLEncodeStringFromString:ad_password];
      ad_params = [[NSString alloc] initWithFormat:@"ad_user=%@&ad_password=%@",ad_user,password];
      NSString *str = [[NSString alloc] initWithFormat:@"%@?&%@",str1,ad_params];
      [request setURL:[NSURL URLWithString:[NSString stringWithFormat:@"%@",str]]];
      [request setHTTPMethod:@"POST"];
      [request setValue:postLength forHTTPHeaderField:@"Content-Length"];
      [request setTimeoutInterval:240];
      [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
      [request setHTTPBody:data];
      NSURLSession *session = [NSURLSession sharedSession];
      NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
      if(error!=NULL)
      {                                                
        NSLog(@"error=%@",error.localizedDescription);
      }
      else
      {
        [self performSelector:handler withObject:data afterDelay:0];
      }
   }];

    [task resume];
}

}

-(void)handler1:(id )data{
//lines of code to execute
}

-(void)handler2:(id )data{
//lines of code to execute
}

I found a fix. i used performSelector:withObject: like @skyylex suggested. also i changed the type of handler from SEL to NSString and did this [self performSelector:(NSSelectorFromString(handler)) withObject:data]; it worked.