UITableView shows nothing

I created a class called "RetrieveDataFromDBTableVC" and set the table view controller's custom class to "RetrieveDataFromDBTableVC".

I think the delegate and data source already set up for me, so I do not need to set again right? (The connection of delegate and datasource is Table View).

In "RetrieveDataFromDBTableVC" class I defined like the following:

  - (void)viewDidLoad
  {
    [super viewDidLoad];
    [self retrieveData];
  }

  -(void)retrieveData
  {
      NSURL * url = [NSURL URLWithString:getDataURL];
      NSData * data = [NSData dataWithContentsOfURL:url];

      citiesArray = [[NSMutableArray alloc]init];

      // Assign data
      NSString * cID = @"aa";
      ...

      cities * myCity = [[cities alloc]initWithCityID:cID andCityID:cName andCityState:cState andCityPopulation:cPopulation andCityCountry:cCountry];

      // Add city object to our cities array
      [citiesArray addObject:myCity];

      // Create a myTableView outlet for this table view to reload data 
      // self.tableView is also correct right?
      [self.myTableView reloadData];
   }

   - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:    (NSInteger)section
   {
      // It will not run this function !!
      return [citiesArray count];
   }

   // It will not go into this function either !!
   - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
  {
     // Set the identifier name in UITableViewCell also
     static NSString *CellIdentifier = @"cities";
     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

     // Retrieve the current city object for use with this indexPath.row
    cities * currentCity = [citiesArray objectAtIndex:indexPath.row];

    cell.textLabel.text = currentCity.cityName;

    return cell;
  }