Objective-C, iOS SDK, NSMutableArray, add elements and save data - objective-c

Question

Basically, every time I enter something in my textfield and save it to the table, the previous entry will be replaced by the new one. How do I add elements in a mutable array and save the last entry? I tried
[tabledata addObject....
and in the entry
tabledata.lastObject objectAtIndex...
but that didn't work.
here is what I have:
-(void)viewDidLoad
{
[super viewDidLoad];
titlestring = [[NSUserDefaults standardUserDefaults] objectForKey:#"titlehomework" ];
detailsstring = [[NSUserDefaults standardUserDefaults] objectForKey:#"detailshomework"];
tabledata = [[NSMutableArray alloc] initWithObjects:titlestring, nil];
tablesubtitles = [[NSMutableArray alloc] initWithObjects:detailsstring, nil];
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section;
{
return [tabledata count];
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath;
{
UITableViewCell *cell = nil;
cell = [tableView dequeueReusableCellWithIdentifier:#"homeworkcell"];
if(cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:#"homeworkcell"];
}
cell.textLabel.text = [tabledata objectAtIndex:indexPath.row];
cell.detailTextLabel.text = [tablesubtitles objectAtIndex:indexPath.row];
cell.textLabel.font = [UIFont systemFontOfSize:14.0];
cell.textLabel.backgroundColor = [ UIColor clearColor ];
cell.detailTextLabel.backgroundColor = [UIColor clearColor];
//-----------------------------------------START----------------------------Set image of cell----
cellImage = [UIImage imageNamed:#"checkboxblank.png"];
cell.imageView.image = cellImage;
//--------------------------------------------END---------------------------end set image of cell--
return cell;
}

Answer 1

Without seeing more code, the best I can do is suggest something like this
[tabledata addObject:newTitle];
[tablesubtitles addObject:newSubtitle];
[tableView reloadData];
This assumes both newTitle and newSubtitle are the NSStrings you wish to add and that tableView is the pointer to the UITableView.