Loading Cells' Accessory State from NSUserDefaults - ios

Question

This is how I am currently saving the state of the cell checkmark (which works):
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {\
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
if (cell.accessoryType == UITableViewCellAccessoryNone) {
cell.accessoryType = UITableViewCellAccessoryCheckmark;
[defaults setBool:YES forKey:cell.textLabel.text];
} else {
cell.accessoryType = UITableViewCellAccessoryNone;
[defaults setBool:NO forKey:cell.textLabel.text];
}
[defaults synchronize];
}
This is how I am attempting to retrieve them:
-(void)viewWillAppear:(BOOL)animated {
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
for (int section = 0; section < [self.tableView numberOfSections]; section++) {
for (int row = 0; row < [self.tableView numberOfRowsInSection:section]; row++) {
NSIndexPath* cellPath = [NSIndexPath indexPathForRow:row inSection:section];
UITableViewCell* cell = [self.tableView cellForRowAtIndexPath:cellPath];
if (![defaults valueForKey:cell.textLabel.text]) {
cell.accessoryType = UITableViewCellAccessoryCheckmark;
} else {
cell.accessoryType = UITableViewCellAccessoryNone;
}
}
}
}
The NSUser defaults are saving correctly (I know this because of NSLog), but when I exit and return to the table view, no cells have checkmarks.
If I change the line:
if (![defaults valueForKey:cell.textLabel.text]) {
to
if ([defaults valueForKey:cell.textLabel.text]) {
the table view reappears with all cells having checkmarks.
Thanks

Answer 1

Your problem is that [self.tableView cellForRowAtIndexPath:cellPath]; can return nil if there is currently no cell for that row in the table - which is almost certainly the case in viewDidLoad because the view isn't visible yet. Even if the table has loaded that method can still return nil if the cell has scrolled out of view and the cell object has been released or reused.
You would be better storing your selection state in an NSMutableDictionary and storing the dictionary in NSUserDefaults. You can then check the contents of the dictionary in cellForRowAtIndexPath and set the accessory accordingly.