Wrong object added to UITableView - ios

Question

In my app I get an object by NSNotificationCenter (form another controller) and add the object to UITableView:
-(void)viewWillAppear:(BOOL)animated
{
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(RosterSave:) name:#"RosterSave" object:nil];
}
-(void)RosterSave:(NSNotification *)notification
{
NewRoster* newRoster = [[NewRoster alloc]init];
newRoster = notification.object;
[myUser.rosterArray addObject:newRoster];
[self.myRoster reloadData];
}
This is the tableView method:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return myUser.rosterArray.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *iden = #"MyTable";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:iden];
if (cell == nil)
{
cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:iden];
}
NewRoster* myNewRoster = [myUser.rosterArray objectAtIndex:indexPath.row];
cell.textLabel.text = myNewRoster.nameRoster;
return cell;
}
When the user adds the first object, the tableView get own row. When the user adds the second object, it adds two rows of the second object and on this way.
How can I fix this issue?

Answer 1

You have add observer(notification) in viewWillAppear which get called everytime when view will appear.
add notification in viewDidLoad instead of viewwillAppear.

Answer 2

I always like to put NSNotification subscriptions in init / and unsubscriptions in dealloc. This pattern is easy to read and debug. Also, it guarantees you will never double subscribe or double unsubscribe.
In your case, you are prone to creating multiple subscribtions in viewWillAppear
- (instancetype)init
{
...
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(RosterSave:) name:#"RosterSave" object:nil];
...
}
- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}

Answer 3

#Feroz is right about you allocating a new object and replacing it with notification.object. #Lion is right about viewDidLoad vs. viewDidAppear You are generating multiple notifications. You need to only generate one per object. Put a breakpoint in your RosterSave code and count how many times it's called per new object. Also look at the stack trace to see who is generating these calls. It's down to a simple matter of stepping through, understanding your code, and seeing what's happening.