reloadData is stacking ontop of old data - ios

Question

I understand that I need to change the data in the data source before calling reloadData. My problem is that I'm not sure how this is done and why my getData method doesn't overwrite the current cells. Is it necessary to use subviews for this? Or is there a way to reset the cells when refresh is called to just create a new set of data?
#property (nonatomic,strong) NSMutableArray *objectHolderArray;
#end
#implementation MartaViewController
- (void)viewDidLoad
{
[super viewDidLoad];
[self getData];
//to add the UIRefreshControl to UIView
UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
refreshControl.attributedTitle = [[NSAttributedString alloc] initWithString:#"Please Wait..."];
[refreshControl addTarget:self action:#selector(refresh:) forControlEvents:UIControlEventValueChanged];
}
- (void)getData
{
NSURL *blogURL = [NSURL URLWithString:JSON_URL];
NSData *jsonData = [NSData dataWithContentsOfURL:blogURL];
NSError *error = nil;
NSDictionary *dataDictionary = [NSJSONSerialization
JSONObjectWithData:jsonData options:0 error:&error];
for (NSDictionary *bpDictionary in dataDictionary) {
Object *currenHotel = [[Object alloc]Station:[bpDictionary objectForKey:#"station"] Status:[bpDictionary objectForKey:#"status"]];
[self.objectHolderArray addObject:currenHotel];
}
}
- (IBAction)refresh:(UIRefreshControl *)sender {
[self getData];
[self.tableView reloadData];
[sender endRefreshing];
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:
(NSInteger)section
{
return [self.objectHolderArray count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:
(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
MartaViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier
forIndexPath:indexPath];
Object *currentHotel = [self.objectHolderArray
objectAtIndex:indexPath.row];
cell.lblStation.text = currentHotel.station;
cell.lblStatus.text = currentHotel.status;
return cell;
}
-(NSMutableArray *)objectHolderArray{
if(!_objectHolderArray) _objectHolderArray = [[NSMutableArray alloc]init];
return _objectHolderArray;
}
#end

Answer 1

Because you are adding objects to self.objectHolderArray instead of overwriting in getData method. Try this
- (void)getData
{
NSURL *blogURL = [NSURL URLWithString:JSON_URL];
NSData *jsonData = [NSData dataWithContentsOfURL:blogURL];
NSError *error = nil;
NSDictionary *dataDictionary = [NSJSONSerialization
JSONObjectWithData:jsonData options:0 error:&error];
[self.objectHolderArray removeAllObjects];
for (NSDictionary *bpDictionary in dataDictionary) {
Object *currenHotel = [[Object alloc]Station:[bpDictionary objectForKey:#"station"] Status:[bpDictionary objectForKey:#"status"]];
[self.objectHolderArray addObject:currenHotel];
}
}

Answer 2

First initialize the array in viewDidLoad self.objectArray = [NSMutlabelArray alloc] init] and when you are refreshing the table view remove all objects from object array using [self.orderArray removeAllObject] the copy new content in new array.