iOS/Objective-C : Remove Array Item in UserDefault

Question

I have a problem with removing an item from an array which is saved in the user defaults.

Example: I have a list in a table with 8 Names. When I select a row, it will be stored in the userdefault, because when I continue and go back it should stay selected. This works fine, but when I deselect the row, it should be removed from the UserDefaults. How can I do that?

I store the selected rows in this way:

 [selectedRow insertObject:[NSNumber numberWithInt:indexPath.row] atIndex:arrayIndex];
 [userDefaults setObject:selectedRow forKey:@"sight_selectedRow"];

The arrayIndex variable increments everytime when I select a row. The Array has a capacity of 8.

I thought something like: when I press the 4th row, check the UserDefault array items, is there a 4? If so, delete this item. But I fail to delete THIS item.

Thanks :)

P.S. I use Xcode 5

Answer 1

   /* You should save array of selected row indexes to user default like this */
    // if first time, create arrSelectedRows array
NSMutableArray * arrSelectedRows = [NSMutableArray new];
    // is not first time, load array from userDefaults
arrSelectedRows = [userDefaults objectForKey:@"sight_selectedRow"];
    // when user selects row at indexPath
NSNumber * index = [NSNumber numberWithInt:indexPath.row]];
if (arrSelectedRows containsObject:index]) {
    [arrSelectedRows removeObject:index];
}
else {
    [arrSelectedRows addObject:[NSNumber numberWithInt:index]] ;
}
[userDefaults setObject:arrSelectedRows forKey:@"sight_selectedRow"];
[userDefaults synchronize];

Answer 2

try this, this works for me. make BOOL property isSelected for each cell if isSelected == YES it's add item to NSUserDefaults, otherwise NO.

in your method tableView:didSelectRowAtIndexPath: type this

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
//your code
isSelected = !(isSelected);
}

Answer 3

In place of insertObject, you can use removeIndex property of array for this.

Answer 4

I would suggest you always maintain an array of 8 objects and signal that a selection is invalid using -1.

Therefore when you first start, and there are no selections, the array is:

@[ @(-1), @(-1), @(-1), @(-1), @(-1), @(-1), @(-1), @(-1) ]

When updating the array, you replace (instead of inserting) the selection using:

[selectedRow replaceObjectAtIndex:arrayIndex
                       withObject:@(indexPath.row])];

and, of course, any single change to the array requires the entire array to be written to user defaults:

[userDefaults setObject:selectedRow
                 forKey:@"sight_selectedRow"];

(which you are already doing).

I think you will find this approach to be simpler in the long run as you don't need to worry about the array overflowing your limit of 8 selections.

Answer 5

Try this:

NSMutableArray *tempArray = (NSMutableArray*)[userDefaults objectForKey:@"sight_selectedRow"];;
[tempArray removeObject:unselectedRow];
[userDefaults setObject:tempArray forKey:@"sight_selectedRow"];

Answer 6

I don`t really understand the need to save this in a separate array if you already have your Array.Add a global int value that will keep the row of the chekedItem, at the begining loop through the array or use if else statement or switch statement because you have just 8 items, and see if something is selected if not set chekedItem to 0 (first item in your array)...on didSelectRowAtIndexPath set the chekedItem = indexPath.row. When saving, save the item in array under the chekedItem index.

at the beginning:

  NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];    
  NSString *unit = [userDefaults objectForKey:@"unit"];  
  if ([unit isEqualToString:@"Celsius"]) 
  {
      checkedCellIndex = 0;
  } 
  else 
  {
    checkedCellIndex = 1;
  } // i have just 2 elements in my array

in the didSelectRowAtIndexPath:

    checkedCellIndex  = indexPath.row;
    [tableViewUnits reloadData];

on saving

 NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];        
 switch (checkedCellIndex) {           
    case 0:   
        [userDefaults setObject:@"Celsius" forKey:@"unit"];
        break;   
    case 1:     
        [userDefaults setObject:@"Fahrenheit" forKey:@"unit"];
        break;            

    default:            
        break;